Chemical PapersDOI: 10.2478/s11696-013-0312-1

REVIEW

Carbonised polyaniline and polypyrrole: towards advancednitrogen-containing carbon materials

aGordana Ciric-Marjanovic*, aIgor Pašti, aNemanja Gavrilov,bAleksandra Janoševic, a,cSlavko Mentus

aFaculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, 11158 Belgrade, Serbia

bFaculty of Pharmacy, University of Belgrade, Vojvode Stepe 450, 11221 Belgrade, Serbia

cSerbian Academy of Sciences and Arts, Knez Mihajlova 35, 11000 Belgrade, Serbia

Received 7 August 2012; Revised 20 October 2012; Accepted 22 October 2012

Polyaniline (PANI) and polypyrrole (PPY) undergo carbonisation in an inert/reduction atmo-sphere and vacuum, yielding different nitrogen-containing carbon materials. This contribution re-views various procedures for the carbonisation of PANI and PPY precursors, and the characteristicsof obtained carbonised PANI (C-PANI) and carbonised PPY (C-PPY). Special attention is paid tothe role of synthetic procedures in tailoring the formation of C-PANI and C-PPY nanostructuresand nanocomposites. The review considers the importance of scanning and transmission electronmicroscopies, XPS, FTIR, Raman, NMR, and EPR spectroscopies, electrical conductivity and ad-sorption/desorption measurements, XRD, and elemental analyses in the characterisation of C-PANIsand C-PPYs. The application of C-PANI and C-PPY in various fields of modern technology is alsoreviewed.c© 2013 Institute of Chemistry, Slovak Academy of Sciences

Keywords: polyaniline, polypyrrole, carbonisation, N-containing carbon materials

Introduction

The last two decades have witnessed a tremen-dous development in carbon-based technologies, con-fronting the scientific community with a number ofchallenges regarding the development of new carbon-based advanced materials. Widespread applicabilityhas been found for carbon materials such as carbonblacks, activated carbon materials, pyrolytic carbonmaterials, graphites, glass-like carbon materials, car-bon fibres and filaments, etc., in modern technology.Carbon-based nanomaterials have presented an activefield of research since the first discoveries of Buckmin-sterfullerene C60 by Kroto et al. (1985) and carbonnanotubes (CNTs) by Iijima (1991). Since that time, alarge number of different carbon nanostructures havebeen reported, such as carbon nanospheres, nanofi-bres (CNFs), nanosheets, nanohorns, nanocages, etc.

(Nxumalo & Coville, 2010). Graphene, representinga conceptually new class of two-dimensional carbonmaterials that are only a single atom thick, is arapidly rising star in materials science; it exhibits ex-ceptionally high crystal and electronic qualities andhas already found numerous new potential applica-tions (Geim & Novoselov, 2007).In addition to the attractive properties of shaped

nanocarbon materials, heteroatom doping, defined asthe intentional introduction of foreign atoms such asboron, phosphorus and especially nitrogen, into thestructure of the carbon nanomaterial, can further sig-nificantly affect their unique chemical, mechanical,and electronic properties. This kind of modification ofcarbon material by N and B was achieved for the firsttime by Stephan et al. (1994) using an arc dischargeprocedure. Although reported at the same time, N-doped carbon materials have received much more at-

*Corresponding author, e-mail: gordana@ffh.bg.ac.rs

ii G. Ciric-Marjanovic et al./Chemical Papers

Fig. 1. Types of N-functionalities introduced in C—C/C——Cbond network in shaped nanocarbon materials: pyri-dinic (I ), pyrrolic (II ), quaternary (III ), and pyridineN-oxide nitrogen (IV ).

tention than B-doped carbon materials. Two aspectsof incorporation of the N atom into the network ofC—C/C——C bonds should be considered. The first isthe nature of nitrogen functionalities and the secondrelates to the specific properties rendered by the intro-duction of specific types of N-functionalities into thestructure. Three major structural moieties (Fig. 1) canbe identified as pyridine-like N (I ), pyrrole-like N (II ),and quaternary N (III ), where the graphitic C atomis replaced by the N dopant atom. Besides these threetypes of N-functionalities, pyridine N-oxide nitrogenis also reported (IV ).Once introduced, the N dopant atom inevitably

modifies the local electronic structure and affects thephysical and chemical properties of a new N-dopedcarbon material. To date, it has been shown that themodification of carbon material by N-doping alters thecatalytic properties (Long et al., 2012), charge stor-age characteristics (Gavrilov et al., 2012c), mechanicalproperties (Ganesan et al., 2010), electrical conductiv-ity (Villalpando-Paez et al., 2006), and so on. Many re-searchers have welcomed the possibility of tuning thephysical and chemical properties of carbon materialby the incorporation of nitrogen, while N-containingcarbon materials have found numerous areas of prac-tical application; e.g., N-containing CNTs (NCNTs)are being considered as one of the most promising newelectrocatalysts with a performance similar to that ofplatinum (Gong et al., 2009).The problem of nitrogen incorporation into car-

bon materials remains the focus of numerous in-vestigations. With regard to the production of NC-NTs, the most commonly used procedure is chemi-cal vapour deposition (CVD) (Dupuis, 2005); how-ever, other techniques, such as magnetron sputter-ing (Hellgren et al., 1999), laser ablation (Hu et al.,1998), and pyrolysis of N-containing molecules andmacromolecules (Maiyalagan & Viswanathan, 2005)are also in use. Each technique leads to differenttypes of nitrogen functionalities, as well as differentamounts of nitrogen built within the structure andmorphology of the N-containing carbon material ob-tained. Although high concentrations of nitrogen wereobtained using the magnetron sputtering technique

Fig. 2. Number of articles devoted to carbonised polyanilinesand polypyrroles, published by the ACS, Wiley, Else-vier, RSC, Springer, Taylor & Francis, IOP, from 1999to July 2012.

(up to 26 mole % (Hellgren et al., 1999)), it repre-sents a challenge to obtain N-doped carbon materi-als with more than 10 mole % of nitrogen by othermethods. A further challenge is encountered in therequirements for large-scale production, as sophisti-cated equipment is commonly required. Carbonisationof N-containing aromatic polymer materials such asPANI and PPY has emerged in recent years (Fig. 2) asan efficient way to prepare N-containing carbon ma-terials/nanomaterials, most frequently with the pre-served morphology of the PANI and PPY precursors.The polymeric precursor itself can be prepared un-der moderate and well-controlled conditions by us-ing both template-based and template-free methods(Ciric-Marjanovic, 2010), while the choice of carboni-sation method, temperature, and duration, as well asthe composition of the gas atmosphere represents anadditional degree of freedom in the fabrication of car-bon material.In this contribution, PANI and PPY-derived N-

containing carbon materials are considered from theaspects of synthesis, characterisation and application.Recent advances in this field are summarised to pro-vide a comprehensive overview of the large amount ofwork completed to date and an insight into the richworld of carbonised PANI and PPY micro- and nanos-tructures. Special emphasis is given to the applicationof this class of materials as a key inspiration for cur-rent research.

Synthesis

Carbonised PANI

Carbonisation of PANI was performed under a va-riety of conditions. Heating in inert atmosphere (N2,Ar, He), reduction atmosphere (N2 containing 5 %of H2 or Ar containing 5 % of H2), or in vacuum at

G. Ciric-Marjanovic et al./Chemical Papers iii

constant temperature, e.g., 300◦C (Yin et al., 2010b),400◦C (Stejskal et al., 2007; Lei et al., 2009b; Yin etal., 2010b), 500◦C (Langer & Golczak, 2007; Lei et al.,2009b; Yin et al., 2010b; Kuo et al., 2012; Hsu & Kuo,2012), 550◦C (Lei et al., 2009b; Jin et al., 2010; Yinet al., 2011, 2012), 600◦C (Stejskal et al., 2007; Lei etal., 2009a; Yin et al., 2010b; Yuan et al., 2011; Wu etal., 2011; Hsu & Kuo, 2012), 650◦C (Lei et al., 2009b;Stejskal et al., 2010; Hsu & Kuo, 2012), 700◦C (Wanget al., 2008b; Li et al., 2010d; Yin et al., 2010b; Yuanet al., 2011; Kuo et al., 2012; Jiang & Jiang, 2012; Guet al., 2012), 750◦C (Lei et al., 2009b), 800◦C (Choi etal., 2007; Langer & Golczak, 2007; Yin et al., 2010b;Yuan et al., 2011; Kuo et al., 2012; Hsu & Kuo, 2012),850◦C (Qiu et al., 2009; Jin et al., 2010; Yan et al.,2010; Wu et al., 2011; Chen et al., 2011b, 2012a; Kim& Park, 2012a, 2012b), 900◦C (Lin et al., 2008; Wu etal., 2008c, 2011; Yuan et al., 2011; Kuo et al., 2012;Tan et al., 2012), 950◦C (Lei et al., 2009a, 2009b; Wuet al., 2011), 1000◦C (Doh et al., 2006; Kyotani et al.,2008; Wu et al., 2011), 1100◦C (Langer & Golczak,2007), 1150◦C (Cao et al., 2012), and 1200◦C (Zhu etal., 2009) are common methods of PANI carbonisa-tion. Carbonisation in air, accompanied by combus-tion, was reported rarely (Stejskal et al., 2005, 2007;Trchová et al., 2006; Zhou et al., 2012). Pre-heating(stabilisation) of PANI was performed in some cases,e.g., 1 h at 270◦C (Qiu et al., 2009), 2 h at 300◦C(Chen et al., 2011b), 2 h at 400◦C (Yang et al., 2010),and 5 h at 400◦C (Gu et al., 2012).PANI was most frequently carbonised at a constant

temperature for 2 h (Doh et al., 2006; Trchová et al.,2006; Stejskal et al., 2007; Langer & Golczak, 2007;Lin et al., 2008; Qiu et al., 2009; Li et al., 2010d, Jinet al., 2010; Yan et al., 2010; Yuan et al., 2011; Chenet al., 2011b, 2012a; Kim & Park, 2012a, 2012b) or 3 h(Choi et al., 2007; Lei et al., 2009a, 2009b; Stejskal etal., 2010; Kuo et al., 2012; Hsu & Kuo, 2012). Shorterperiods of time, e.g., 5 min (Zhou et al., 2012) and1 h (Wu et al., 2008c), as well as longer periods, e.g.,4 h (Tan et al., 2012), 6 h (Cao et al., 2012), 12 h(Gu et al., 2012), and 15 h (Jiang & Jiang, 2012) werealso employed for carbonisation of PANI at a constanttemperature.Several research groups applied gradual heating:

ambient temperature (AT) → 300◦C, 15◦C min−1

(Rozlívková et al., 2011); AT → 400◦C, 15◦C min−1

(Rozlívková et al., 2011); AT → 500◦C, 15◦C min−1

(Rozlívková et al., 2011); AT → 600◦C, 4 ◦C min−1

(Xiang et al., 2011d), 15◦C min−1 (Rozlívková etal., 2011); AT → 650◦C, 22◦C min−1 (Morávková etal., 2012b); AT → 700◦C, 4◦C min−1 (Xiang et al.,2011b), 10◦C min−1 (Xiang et al., 2011a), 15◦C min−1

(Rozlívková et al., 2011); AT → 800◦C, 10◦C min−1

(Mentus et al., 2009; Gavrilov et al., 2011b, 2012c;Janoševic et al., 2011, 2012), 15◦C min−1 (Rozlívkováet al., 2011). A combination of gradual heating andconstant temperature heating was also applied by

some investigators: heating from AT to various tem-peratures (300◦C, 400◦C, 600◦C, 800◦C, 1000◦C, and1200◦C) at a heating rate of 3◦C min−1 and main-taining at the final temperature for 2 h (Lu et al.,2011); heating from AT to 700◦C at a heating rateof 5◦C min−1 (Xiang et al., 2011c) or 7◦C min−1 (Liet al., 2011) and maintaining at 700◦C for 2 h; heat-ing from AT to various temperatures (700◦C, 800◦C,and 900◦C) at a heating rate of 5◦C min−1 and main-taining at the final temperature for 2 h (Li et al.,2010c). A combination of gradual heating, preheat-ing (stabilisation), and constant temperature heatingwas occasionally employed: gradual heating from ATto 450◦C at a heating rate of 1◦C min−1 and main-taining at this temperature for 30 min, and then to800◦C at a heating rate of 2◦C min−1 and maintain-ing at this temperature for 2 h (Dai et al., 2011); af-ter stabilisation at 400◦C gradual heating to 600◦C,700◦C, 850◦C, 1000◦C, and 1100◦C at a heating rateof 0.5◦C min−1 and maintaining for 2 h at the finaltemperatures (Yang et al., 2010).Various PANI salts were used as precursors in

the carbonisation process: sulphate/hydrogen sul-phate (Wu et al., 2008c; Mentus et al., 2009; Yanget al., 2010; Li et al., 2010b; Gavrilov et al., 2011b,2012b, 2012c; Kuo et al., 2012; Morávková et al.,2012b; Hsu & Kuo, 2012), hydrochloride (Dai et al.,2011; Kim & Park, 2012a; Morávková et al., 2012a,2012b; Zhou et al., 2012; Chen et al., 2012a; Trchováet al., 2012), dihydrogen phosphate (Li et al., 2010d;Jiang & Jiang, 2012; Gu et al., 2012), perchlorate(Yin et al., 2012), acetate (Trchová et al., 2009; Xi-ang et al., 2011c), succinate (Trchová et al., 2009),D,L-tartrate (Cao et al., 2012), citrate (Yin et al.,2010b, 2011), 3,5-dinitrosalicylate (DNSA) (Gavrilovet al., 2012c; Janoševic et al., 2012), 5-sulphosalicylate(SSA) (Janoševic et al., 2011; Gavrilov et al., 2012c),D-camphorsulphonate (Kyotani et al., 2008), and lig-nosulphonate (Lu et al., 2011). Carbonisation of aPANI emeraldine base was also investigated. A highenergy (MeV) ion-irradiated PANI base showed atransition from an insulating state to a carbonisedPANI conducting state (Park et al., 2004). Structuraland conductivity changes during pyrolysis of the PANIbase were investigated for the first time by Trchováet al. (2006). PANI base carbonisation was recentlystudied by Li et al. (2010d, 2011), Rozlívková et al.(2011), Xiang et al. (2011b, 2011d), and Morávkováet al. (2012a, 2012b).Template methods were used in order to prepare

ordered microporous and mesoporous N-containingcarbon materials as well as hollow N-containing car-bon spheres from PANI precursors. N-containing or-dered mesoporous carbon materials were nanocastfrom mesoporous silica SBA-15 using PANI as car-bon precursor (Lei et al., 2009a). Mesoporous N-containing activated carbon materials were preparedusing PANI as a carbon source via the nano-sized

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Fig. 3. Scheme of preparation of N-containing carbon nanotubes (N-CNTs) by carbonisation of PANI–silica nanotube composite(S-NT–PANI) and silica etching. Ultimately, N-CNTs were chemically activated using KOH to produce AC-N-CNTs.(Reprinted with permission from Kim & Park (2012b). Copyright 2012 Elsevier).

silica template method (Kim & Park, 2012a). Meso-pores are formed by silica etching. Similarly, micro-porous C-PANI nanotubes (C-PANI-NTs) have re-cently been synthesised using silica nanotubes as atemplate (Kim and Park (2012b), Fig. 3). HollowN-containing carbon spheres were synthesised usingsulphonated polystyrene spheres as a core templateand PANI shell as the carbon source (Dai et al.,2011). The morphology, diameter, and wall thicknessof the hollow carbon spheres were tuned by varying thesulphonation rate of the polystyrene core template.Activation of C-PANI was achieved using a variety

of activating agents in order to obtain C-PANI withthe largest possible specific surface area. Xiang et al.(2011a) prepared activated C-PANI by using ZnCl2as an activating agent. Li et al. (2010d, 2011) acti-vated C-PANI derived from a PANI base with H3PO4or KOH at 700◦C for 2 h under N2. An activated N-containing carbon material was also prepared from aPANI base using K2CO3 as an activating agent (Xi-ang et al., 2011d, 2011b). KOH was most frequentlyused for activation of C-PANI (Qiu et al., 2009; Yanet al., 2010; Li et al., 2010d, 2011; Gavrilov et al.,2011b; Chen et al., 2011b, 2012a; Kim & Park, 2012b).It was found that the specific surface area of theC-PANI-NTs (217 m2 g−1) increased significantly to1958 m2 g−1 with chemical activation by KOH solu-tion (Kim & Park, 2012b).

Carbonised granular PANI

The carbonisation of a granular PANI base to pro-duce N-containing carbon material was reported byTrchová et al. (2006) and Rozlívková et al. (2011).The PANI base was carbonised in an inert atmosphereat temperatures up to 800◦C for various times (Ro-zlívková et al., 2011). The mass decreased to 40–50mass % at temperatures above 600 ◦C. Carbonisationat 650◦C for 1 h was proposed for the optimum con-version of PANI to carbon material. The product re-tained the original globular structure of PANI. Theconductivity of the carbonised material was low for

carbonisations below 600◦C, < 10−10 S cm−1, and in-creased to 10−4 S cm−1 after treatment at 800◦C. Thenitrogen content, ≈ 10 mass %, was not appreciablyaffected by the carbonisation.

Carbonised PANI films

Protection of cellulose fibres and wood with PANIfilm coatings against heat exposure and fire wasdemonstrated by Stejskal et al. (2005, 2007). ThePANI-coated filtration paper was ignited with a matchand left to burn (Stejskal et al., 2005), while the PANI-coated wood was placed in a flame or in a furnace op-erating at 400◦C or 600◦C in the ambient atmosphere(Stejskal et al., 2007), and the mass loss was deter-mined. It was found that the burned PANI-coatedfiltration paper material retained the original fibril-lar morphology of cellulose and the PANI film coatingwas converted to solid carbon products (Stejskal et al.,2005). The wood coated with PANI was less reducedin its mass than uncoated samples and was convertedto charcoal rather than to ash due to carbonisationof the PANI film coatings. Carbonisation of PANI–H2SO4 film on CNT (Kuo et al., 2012), PANI base andPANI–HCl/PANI–H2SO4 on multi-wall carbon nano-tubes (MWCNT) (Morávková et al., 2012b) was re-ported. PANI hydrochloride and PANI base films de-posited on silicon and ceramic supports were heatedup to 500◦C in a nitrogen atmosphere (Morávková etal., 2012a; Trchová et al., 2012). Transformation fromPANI salt to the base form was detected above 100◦C.The conversion to N-containing carbon-like materialfollowed at temperatures above 200◦C (Morávková etal., 2012b). At temperatures of 600◦C and higher, nofilms of carbonised PANI were found on the supports.The lower thermal stability of the PANI films, in com-parison with granular and nanostructured PANI pow-ders, has been explained by their low mass, of theorder of tens of µg cm−2, and their possible degra-dation by traces of oxygen in the carrier gas overthe longer duration of experiments at higher temper-atures.

G. Ciric-Marjanovic et al./Chemical Papers v

Fig. 4. SEM (A, B, C) and TEM (A1, A2, B1, B2, C1, C2) images of samples obtained by carbonisation of PANI·SSA (A, A1, A2),PANI·sulphfate/hydrogensulphfate, produced by template free-dopant free polymerisation (B, B1, B2), and PANI·DNSA(C, C1, C2). (Reprinted with permission from Gavrilov et al. (2012c). Copyright 2012 Elsevier).

vi G. Ciric-Marjanovic et al./Chemical Papers

Carbonised PANI nanostructures

Nanometric sponge-like structures were preparedby the carbonisation of PANI emeraldine salt usinga rapid immersion in a hot-filament system fed withcarbon dioxide, ethyl alcohol, and argon (Baranauskaset al., 2007). Highly carbonised PANI micro- andnanotubes as a new, thermally stable nanomate-rial for nanosensors and nanodevices with a widerange of possible applications, comparable with car-bon nanotubes, were first prepared by Langer & Gol-czak (2007). Carbonised products had the same mor-phology as the starting PANI micro- and nanotubes,but a lower spin density. A tubular-shaped nanocar-bon was prepared by pyrolysis of the tubular-shapedself-assembled PANI D-camphorsulphonate (Kyotaniet al., 2008). A nanotubular/nanofibrous PANI, pre-pared from an emulsion polymerisation in the pres-ence of n-dodecylbenzene sulphonic and hydrochloricacids, was deprotonated and exposed to gradual heat-ing from AT to 800◦C in argon (Ho et al., 2009), lead-ing to the formation of C-PANI nanosheets at T ≤800◦C and C-PANI nanoparticles at T > 800◦C. In or-der to deprotonate and carbonise the PANI nanotubes(PANI-NTs), Murai et al. (2009) performed a heattreatment of PANI-NTs up to 1200◦C in a microwaveheating system in the presence of carbon fibres. PANI-NTs, prepared by the oxidation of aniline in solutionsof acetic or succinic acids, were carbonised duringthermogravimetric analysis (Trchová et al., 2009). Thenanotubular morphology of PANI was preserved af-ter carbonisation. Conducting NCNTs, accompaniedby nanorods and nanosheets, were synthesised by thecarbonisation of self-assembled nanostructured PANIsulphate/hydrogensulphate, prepared by the dopantfree-template free method (Mentus et al. (2009) andGavrilov et al. (2011a, 2011b, 2012c), Figs. 4B, 4B1,and 4B2). NCNTs with open-end and low specific sur-face area were prepared via the carbonisation of PANI-NTs synthesised by a rapidly mixed reaction (Yang etal., 2010). CNTs with a large surface area and surfacenitrogen and oxygen functional groups were preparedby carbonisation and activation of PANI-NTs, whichwere synthesised by polymerisation of aniline by theself-assembly method in aqueous media in the pres-ence of acetic acid (Xiang et al., 2011c). A series ofrectangular PANI-NTs, synthesised using hollow car-bon nanosphere templates, were recently carbonisedand activated with KOH (Chen et al., 2011b). NC-NTs were prepared through carbonisation of a PANIcitrate (Yin et al., 2010b) and PANI D,L-tartrate nan-otube precursor (Cao et al., 2012).Microporous NCNTs were prepared via the car-

bonisation of silica–PANI-NTs composites (Kim &Park, 2012b). After carbonisation of silica nanotubescoated with PANI and silica etching, the NCNTswere chemically activated using a KOH solution.Micro/mesoporous conducting N-containing carbon

nanorods/nanotubes with high surface area were syn-thesised by the carbonisation of self-assembled PANI5-sulphosalicylate (PANI·SSA) nanorods/nanotubes(Janoševic et al. (2011) and Gavrilov et al. (2012c),Figs. 4A, 4A1, and 4A2). The morphology of thePANI·SSA was preserved after carbonisation.Microporous conducting N-containing carbon nano-

rods, with a disordered graphite-like structure, haverecently been synthesised by the carbonisation ofconducting self-assembled PANI 3,5-dinitrosalicylate(PANI·DNSA) nanorods (Janoševic et al. (2012) andGavrilov et al. (2012c), Figs. 4C, 4C1, and 4C2).N-enriched carbon nanowires were prepared by thecarbonisation method using PANI nanowires as acarbon precursor at different temperatures (Yuanet al., 2011). It was shown by Han et al. (2008)that highly ordered undoped butylthio-functionalisedPANI nanospheres could serve as ideal precursormaterials for creating concentric graphitic carbonnanospheres at relatively low processing temperatures.The silica-coated PANI colloidal nanospheres weresubjected to pyrolysis treatment, followed by etchingof the silica with HF to fabricate the N-containing car-bon shells (Lei et al., 2009b). N-containing hollow car-bon nanospheres were prepared by direct pyrolysis ofthe hollow PANI–lignosulphonate spheres at differenttemperatures (Lu et al., 2011). Hollow N-containingcarbon nanospheres were also synthesised by the car-bonisation of sulphonated polystyrene/PANI core/shell spheres (Dai et al., 2011). Owing to the presenceof sufficient sulphonic acid groups on the polystyrenesurface, the difference in the decomposition temper-ature between the PANI shells and the polystyrenecore was increased, resulting in the formation of hollowcarbon spheres with good sphericity and thick carbonshells by carbonising sulphonated polystyrene/PANIcore-shell polymer spheres.

Carbonised PANI-based composites

N-containing carbon materials were successfullysynthesised through the carbonisation of a hybrid-containing traditional carbon black covered by insitu polymerised PANI (Wu et al., 2008b, 2008c).N-modified ordered mesoporous carbon material wassynthesised through carbonisation of PANI-coatedmesoporous carbon material (Guo et al., 2011). CNT–C-PANI nanocomposites were prepared by coatingPANI layers on the CNT core through in situ anilinepolymerisation and subsequent carbonisation (Qiu etal., 2009; Hsu et al., 2010; Jin et al., 2010; Kuo et al.,2012; Morávková et al., 2012b). Core/shell nanostruc-tured carbon materials with carbon nanofibre (CNF)as the core and N-containing graphitic layer as theshell were synthesised by pyrolysis of CNF–PANI com-posites prepared by in situ polymerisation of aniline onCNFs (Zhou et al., 2012). Two-dimensional dielectricsheets composed of graphene-supported amorphous

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Fig. 5. Schematic diagram of synthesis of PANI–M–C catalysts. Mixing of high-surface area carbon with aniline oligomers andtransition-metal precursor (M: Fe and/or Co) (A). Oxidative polymerisation of aniline by the addition of APS (B). Firstheat treatment in N2 atmosphere (C). Acid leaching (D). (Reprinted with permission from Wu et al. (2011). Copyright2012 AAAS).

carbonised PANI were recently prepared by annealingPANI-coated graphene oxide sheets in vacuum (Yinet al., 2012). A C-PANI–graphene composite whichshowed a 2D plate structure and crystallinity similarto that of pristine graphene was prepared by coatingthe graphene with PANI by in situ aniline polymeri-sation and subsequent carbonisation (Kim & Park,2011).Si–C composites were prepared by the carbonisa-

tion of PANI coating on silicone powder (Doh et al.,2006). Wu et al. (2011) used PANI as a precursorfor high-temperature synthesis of N-containing car-bon catalysts incorporating Fe and Co (Fig. 5). Aporous carbon material made from PANI with differ-ent ferrocene loadings was prepared through carboni-sation and thermal activation with KOH (Chen et al.,2012a). The ferrocene served as a pore-forming agentand a resource of Fe nanoparticles which were embed-ded in the C-PANI matrix or dispersed on the surface.N-containing carbonised PANI nanotubes/nanosheetswere used to synthesise a novel type of supported

Pt nanoparticles electrocatalyst PtNPs–C-nanoPANI(Gavrilov et al., 2011a). The Pt/C–PANI-MWCNTcomposites were recently synthesised by chemical oxi-dation polymerisation of aniline on CNTs by usingAPS and H2PtCl6 as co-oxidants, followed by com-posite carbonisation (Hsu & Kuo, 2012). Pt/C–PANI-CNT catalyst has also been successfully prepared byembedding Pt nanoparticles inside the pores of theN-containing porous carbon layer surrounding CNTs,obtained by the carbonisation of PANI-CNT compos-ite (Kuo & Hsu, 2011).Manganese dioxide-modified carbonised nanostruc-

tured PANI was prepared via hydrothermal (Šljukic etal., 2011; Mališic et al., 2012) and low-temperaturewet impregnation procedures (Mališic et al., 2012).Fabrication of the MnO-containing mesoporous N-containing carbon nanocomposite by the hydrother-mal synthesis of Mn3O4–PANI core/shell nanoparti-cles from a mixture containing aniline, Mn(NO3)2,and KMnO4, followed by heat treatment and acidleaching, has recently been demonstrated (Tan et al.,

viii G. Ciric-Marjanovic et al./Chemical Papers

Fig. 6. SEM and TEM images of: template-free-synthesised, urchin-like, PANI·perfluorooctane sulphonate hollow spheres (a) and(b); electromagnetically functionalised hollow urchin-like carbon spheres (EMFHRCSs) with a 2 M loading of FeCl3,carbonised at 1200◦C (c) and (d). Electron diffraction pattern of EMFHRCSs in Fig. 6c (e). (Reprinted with permissionfrom Zhu et al. (2009). Copyright 2009 Wiley).

2012). Semi-conducting PANI-NTs–silica nanocom-posites, synthesised by the oxidative polymerisationof aniline with ammonium peroxydisulphate in aque-ous medium in the presence of colloidal silica parti-cles, have preserved their morphology after carboni-sation (Ciric-Marjanovic et al., 2009). The carboni-sation of colloidal PANI particles stabilised with sil-ica nanoparticles led to formation of the C-PANI–SiO2 material containing 77 mass % of silica (Stejskalet al., 2010). Hollow, conductive, urchin-like carbonspheres with ferromagnetic properties were preparedby a carbonisation process by using template-free-synthesised, urchin-like, hollow PANI spheres contain-ing FeCl3 as the precursors (Zhu et al. (2009), Fig. 6).The high conductivity at ambient temperature (12.3S cm−1) resulted from the graphite-like structure,whereas ferromagnetic properties were attributed to

α-Fe or γ-Fe2O3 nanoparticles, produced from FeCl3during the carbonisation.LiFePO4–C-PANI core/shell nanocomposites with

different C-PANI shell thicknesses were synthesisedby a simple two-step procedure which involved thesynthesis of PANI-coated FePO4 and the subsequentcarbonisation of FePO4–PANI in the presence ofCH3COOLi and sucrose (Jiang and Jiang (2012) andWang et al. (2008b), Fig. 7). Carbon-coated LiFePO4cathode materials were also recently successfully syn-thesised by carbonisation of the precursor FePO4–PANI and equimolar quantity of LiOH ·H2O (Gu etal., 2012). The carbonisation of the FePO4–PANIcomposite in the presence of lithium salt, sodium saltand some glucose led to the transformation of thisFePO4–PANI composite into a Li1−xNaxFePO4–C-PANI composite (0 ≤ x ≤ 0.05) (Yin et al., 2010a).

G. Ciric-Marjanovic et al./Chemical Papers ix

Fig. 7. Electron-transfer pathway for LiFePO4 particles partially coated with carbon (a). Designed ideal structure for LiFePO4particles with typical nano-size and a complete carbon coating (b). Preparation process for the LiFePO4–carbon compositeincluding an in situ polymerisation reaction and two typical restriction processes (c). (Reprinted with permission fromWang et al. (2008b). Copyright 2008 Wiley).

Carbonised aniline oligomers

During the thermogravimetric analysis of sphericalaniline oligomers, formed by the oxidation of anilinewith APS in alkaline aqueous solutions, oligoanilinescompletely decompose in air after reaching ≈ 700◦C,while in a nitrogen atmosphere they leave more than50 mass % residue of a carbonised material which hasa sheet-like morphology (Stejskal and Trchová (2012),Fig. 8). The nitrogen content in the original sample(15 mass %) was almost completely preserved aftercarbonisation.

Carbonised PPY

As with PANI, carbonisation of PPY in an inertatmosphere (N2, Ar) or in air at a constant temper-

ature, e.g., 500◦C (Chen et al., 2012b), 600◦C (Ma etal., 2011; Su et al., 2011), 650◦C (Qie et al., 2012),700◦C (Chen et al., 2012b; Kuroki et al., 2012; Yaoet al., 2012), 800◦C (Su et al., 2010; Liao et al., 2010;Liu et al., 2011; Ma et al., 2011; Wang et al., 2011b;Kuroki et al., 2012), 850◦C (Yang et al., 2005; Lezan-ska et al., 2010), 900◦C (Kim et al., 2007, 2008, 2009;Maiyalagan 2008; Wang et al., 2008a; Li et al., 2009;Su et al., 2011; Chen et al., 2012b; Liu et al., 2012;Bae & Jang, 2012; Kuroki et al., 2012), 1100◦C (Liaoet al., 2010; Su et al., 2011; Chen et al., 2012b), and1300◦C (Su et al., 2011) has been a frequently usedcarbonisation method. PPY was carbonised at a con-stant temperature for 0.5 h (Qie et al., 2012), 1 h (Liaoet al., 2010; Su et al., 2011; Kuroki et al., 2012), 2 h(Wang et al., 2008a, 2011b; Su et al., 2010; Liu et al.,2011; Chen et al., 2012b), 3 h (Maiyalagan, 2008; Li

x G. Ciric-Marjanovic et al./Chemical Papers

Fig. 8. Original oligoaniline microspheres (a) and the productafter carbonisation at 650◦C in a nitrogen atmosphere(b). (Reprinted with permission from Stejskal and Tr-chová (2012). Copyright 2012 Wiley).

et al., 2009; Yao et al., 2012), and 5 h (Yang et al.,2005; Kim et al., 2007, 2008, 2009; Liu et al., 2012).Li et al. (2010a) applied gradual heating from AT

to 1000◦C (or 1300◦C) at a heating rate of 10◦C min−1

(or 20◦C min−1). Several research groups applieda combined gradual heating and constant temper-ature method: AT → 1000◦C at a heating rate of10◦C min−1, holding at 1000◦C for 1 h, and coolingto AT (Dong & Jones, 2006); AT → 900◦C at a heat-ing rate of 3◦C min−1, holding at 900◦C for 5 h, andcooling to AT (Shang et al., 2009); AT → 850◦C at aheating rate of 3◦C min−1 and held at 850◦C for 3 h(Jeon et al., 2011); heating from AT up to 300◦C at aheating rate of 1◦C min−1 and additionally to 900◦Cat a heating rate of 3◦C min−1, finally held at 900◦Cfor 1 h (Bae & Jang, 2012); AT→ 500◦C at a heatingrate of 1◦C min−1 and held at 500◦C for 2 h (Chen etal., 2011a); AT → 600 and/or 800◦C at a heating rateof 1◦C min−1 and held at 600 and/or 800◦C for 2 h(Ma et al., 2011). A combination of the stabilisation(preheating), gradual heating and constant tempera-ture methods was also applied in the carbonisation of

PPY, e.g., stabilisation (1◦C min−1 to 300◦C), heating(3◦C min−1 to 900◦C), holding for 1 h, natural cooling(Bae, 2011).Various PPY salts were used as precursors in

the carbonisation process, e.g., sulphate/hydrogensulphate (Ma et al., 2011), hydrochloride (Liao etal., 2010; Wang et al., 2011b), nitrate (Liao etal., 2010; Li et al, 2010a), perchlorate (Liao etal., 2010), dodecylbenzenesulphonate (Chen et al.,2011a), camphorsulphonate (Liao et al., 2010), andp-toluenesulphonate (TSA) (Maiyalagan, 2008).Hard templates, which can be removed by etch-

ing (e.g., dissolution of silica in hydrofluoric acid),were used in order to prepare ordered mesoporous N-containing carbon materials from PPY precursors bytheir carbonisation. A facile synthetic route to orderedmesoporous carbon material, with PPY as carbon pre-cursor and mesoporous silica as template, was devel-oped by Yang et al. (2005) and Fuertes and Centeno(2005). Mesoporous C-PPY was also synthesised byusing silica SBA-15 as a templating agent (Kim et al.,2007, 2009; Lezanska et al., 2010). A synthesis routefor mesoporous C-PPY nanosheets was developed us-ing nanotubes of halloysite, a type of natural clay thatis structurally and chemically similar to kaolinite, astemplate (Liu et al., 2012). N-containing mesostruc-tured cellular foam carbon was synthesised by a tem-plating method using mesostructured cellular foam sil-ica and PPY as a templating agent and a carbon pre-cursor, respectively (Kim et al., 2008). Multi-lamellarvesicular structures have been used as templates forpreparation of their C-PPY replicas (Lezanska et al.,2010).The activation of highly porous C-PPYs was car-

ried out under severe (mass ratio of KOH : PPy =4) or mild (mass ratio of KOH : PPy = 2) activationconditions at different temperatures in the 600–800◦Crange (Sevilla et al., 2011b). Ultra-high surface area(3000–3500 m2 g−1) N-containing carbon materialswere obtained via chemical activation of C-PPY withKOH (Sevilla et al., 2011a). Tuning of the carbon tex-tural properties was achieved through control of theactivation parameters (temperature and amount ofKOH). For chemical activation, C-PPY nanosphereswere mixed with powdered solid KOH at a mass ratioof 1 : 4, and then heated to 900◦C with a heating rateof 5◦C min−1 in N2 and held for 2 h (Su et al., 2010,2011), or C-PPY nanospheres were mixed with KOHat a mass ratio of 1 : 1, and then heated to 900◦Cwith a heating rate of 5 ◦C min−1 in N2 and held for30 min (Liu et al., 2011).

Carbonised PPY microstructures

Partially ordered micrometer-sized N-containingcarbon tubes several centimetres in length were pre-pared by the pyrolysis of composite fibres consist-ing of a thermally more stable PPY skin layer and

G. Ciric-Marjanovic et al./Chemical Papers xi

Fig. 9. SEM images of PPY nanofibre webs (a) and carbonised nanofibre webs (CNFWs) (b). High resolution-TEM image ofCNFWs (c). Nitrogen adsorption–desorption isotherms and pore size distribution (inset) of CNFWs (d). (Reprinted withpermission from Qie et al. (2012). Copyright 2012 Wiley).

a poly(ethylene terephthalate) core (Han et al., 1999,2001a, 2001b). The wall thickness of the resultant C-PPY microtubes was found to be directly proportionalto the thickness of the original PPY coating. Graphi-tisation of a single PPY microtube, accompanied withthe emission of strong visible light from PPY micro-tube, was observed by applying a voltage between thetwo ends of a single PPY microtube (Yan et al., 2005).

Carbonised PPY nanostructures

Jang et al. (2002) showed that N-containinggraphite nanoparticles, with diameters as small as2 nm, could be fabricated by the carbonisation ofPPY nanoparticles of similar dimensions. A simul-taneous thermogravimetry–differential thermal anal-ysis technique demonstrated that the PPY nanopar-ticles can be efficiently carbonised into N-containingcarbon nanoparticles with a narrower size distribu-tion than that of PPY (Li et al., 2010a). PPYnanospheres were carbonised to N-containing carbonnanospheres (Zhang & Manohar, 2006; Wang et al.,2008a; Liao et al., 2010; Su et al., 2010, 2011; Liuet al., 2011). Nanoscale porous N-containing carbonfibres were successfully synthesised by pyrolysis ofPPY, synthesised by the self-degradation templatemethod (Li et al., 2009). N-containing CNF webswith high surface areas were successfully prepared

by carbonisation of PPY nanofibre webs in the pres-ence of KOH (Qie et al. (2012), Fig. 9). Bulk quan-tities of nanocarbon particles having a pre-selectedmorphology (nanofibres, nanotubes, etc.) were syn-thesised using a simple and rapid microwave heat-ing approach directly from doped PPY nanostructures(Zhang & Manohar, 2006). Carbonisation convertedPPY–poly(methyl methacrylate) coaxial fibres into C-PPY nanotubes (C-PPY-NTs) by complete decompo-sition of poly(methyl methacrylate) fibre core and car-bonisation of the PPY wall (Dong & Jones, 2006).NCNTs were obtained by pyrolysis of the PPY nano-tubes, fabricated via a reactive self-degraded tem-plate method (Shang et al., 2009), alumina templatemethod (Maiyalagan, 2008), or surfactant-mediatedmicroemulsion pyrrole polymerisation (Bae & Jang,2012). Fabrication of mesoporous carbonised PPYnanosheets was recently reported (Liu et al., 2012).

Carbonised PPY-based composites

CNFs were prepared through electrospinning ablend solution of polyacrylonitrile and PPY, followedby carbonisation (Ji et al., 2010). N-containing porousCNFs were recently synthesised by carbonisation ofmacroscopic-scale CNFs coated with PPY (Chen etal., 2012b) (Figs. 10 and 11).Sheet-like N-containing C-PPY–graphene compos-

xii G. Ciric-Marjanovic et al./Chemical Papers

Fig. 10. Schematic illustration for fabrication processes of N-containing CNFs. (Reprinted with permission from Chen et al.(2012b). Copyright 2012 ACS).

Fig. 11. FE-SEM images of CNFs and CNFs coated with polypyrrole (CNFs@PPY) (a) and (b). TEM image of carbonisedCNFs@PPY at 900◦C (c). (Reprinted with permission from Chen et al. (2012b). Copyright 2012 ACS).

ites were prepared by carbonisation of a PPY–reduced-graphene-oxide (rGO) composite (Ma et al.,2011). The rGO was used instead of graphene oxide(GO) sheets as a template and a substrate to im-mobilise the PPY since the PPY–GO composite ag-glomerated easily because of the dehydration of ex-cess oxygen-containing groups on the GO sheets dur-ing the drying process. Surface-modified graphitisedcarbon black (GCB) was produced through carboni-sation of PPY on the GCB surface (Jeon et al., 2011).GCB–C-PPY was used as a catalyst support for Ptnanoparticles.Magnetic C-PPY nanostructures were success-

fully obtained by the carbonisation of an iron-dopedPPY precursor (Jang & Yoon, 2003, 2005). Pyrol-ysed iron–PPY mesoporous spheres have been synthe-sised by a template-assisted ultrasonic spray pyroly-sis method (Liu et al., 2009). C-PPY microcapsulescontaining silicon nanoparticles–CNTs nanocompos-ite have been fabricated by a surfactant-mediatedsol–gel method followed by a carbonisation process(Bae, 2011). Three-dimensional SnO2–C-PPY com-posites were prepared via a simple hydrothermal routeand subsequent calcination process using PPY-basedcarbon networks as the support and conductive buffer-ing layer (Mi et al., 2011). The resulting SnO2–C-PPYnetworks were composed of highly flexible, hollow,and end-opening nanofibres which were homogenouslycoated with nanocrystalline SnO2. The N-containinggraphitic layer-coated palygorskite (magnesium alu-minium phyllosilicate) was synthesised by carbonisa-tion of the PPY-coated palygorskite (Wang et al.,

2011b). Core/shell materials with a Fe3O4 core andN-containing carbon shell were prepared using PPYas a carbon precursor (Yao et al., 2012). Pd nanopar-ticles were anchored on the surface without aggrega-tion, thus leading to Pd/C–PPY–Fe3O4 ternary com-posites.

Carbonised PANI-co-PPy

N-containing hollow carbon nanospheres were ef-ficiently prepared by pyrolysis of self-assembled poly(aniline-co-pyrrole) hollow microspheres, formed in anammonia solution via one-step unstirred polymerisa-tion (Lu et al., 2012, Fig. 12).

Characterisation

Morphology

The morphology of PANI precursors was largelypreserved upon carbonisation, as confirmed by SEMand TEM analyses of C-PANIs produced from a gran-ular PANI base (Trchová et al., 2006; Rozlívková et al.,2011), nanotubular PANI base (Trchová et al., 2009),nanotubular PANI salt (Langer & Golczak, 2007; Ky-otani et al., 2008; Mentus et al., 2009; Yin et al.,2010b; Xiang et al., 2011c; Chen et al., 2011b; Cao etal., 2012), PANI salts with morphologies of nanorods(Janoševic et al., 2012; Gavrilov et al., 2012c), nano-tubes/nanorods (Janoševic et al., 2011; Gavrilov et al.,2012c), nanotubes/nanorods/nanosheets (Gavrilov etal., 2011a, 2011b, 2012c), nanowires (Yuan et al.,

G. Ciric-Marjanovic et al./Chemical Papers xiii

Fig. 12. SEM (a) and TEM (b) images of hollow carbon nanospheres. (Reprinted with permission from Lu et al. (2012). Copyright2012 Elsevier).

2011), colloidal PANI nanoparticles (Stejskal et al.,2010), and granular PANI films (Morávková et al.,2012a). This enables the preparation of C-PANIs withthe desired morphologies by pre-selecting the mor-phology of the PANI precursor. Some shrinkage ofnanotubes (Trchová et al., 2009) or granules (Trchováet al., 2006; Morávková et al., 2012a) in C-PANI, re-lated to particles of the starting PANI, as well as someagglomeration of nanorods leading to thicker submi-crofibres in C-PANI (Janoševic et al., 2012) was ob-served. As an exception, a change in morphology wasreported during carbonisation of the PANI emeral-dine base precursor, prepared by an emulsion poly-merisation in the presence of 4-dodecylbenzene sul-phonic and hydrochloric acids, followed by deproto-nation (Ho et al., 2009). The carbonisation at T ≥800◦C led to transformation of the starting nanorodsto C-PANI granular nanoparticles. In contrast withPANI, which generally retains its morphology aftercarbonisation, the microspherical morphology of ani-line oligomers was totally destroyed and replaced bytwo-dimensional sheets (Stejskal & Trchová, 2012).As for PANI, the morphology of PPY precursors,

i.e. nanoparticles (Jang et al., 2002; Li et al., 2010a),nanospheres (Zhang & Manohar, 2006; Wang et al.,2008a; Liao et al., 2010; Su et al., 2010, 2011; Liu et al.,2011), nanofibres (Zhang & Manohar, 2006), nanofi-bre webs (Qie et al., 2012), and nanotubes (Zhang &Manohar, 2006; Shang et al., 2009; Bae & Jang, 2012),was largely preserved upon carbonisation. A certainreduction in particle dimensions compared with theoriginal particle dimensions was observed upon car-bonisation (Zhang & Manohar, 2006; Liao et al.,2010).

Conductivity

The electrical conductivity of C-PANIs has val-ues in a broad range, from ∼ 10−14 S cm−1 (non-conducting) to ∼ 1 S cm−1, depending on the molec-ular structure of the PANI precursor (protonationlevel, i.e. salt or base form, oxidation state, type

Fig. 13. Changes in the conductivity of PANI-NTs after heattreatment. (Reprinted with permission from Yin et al.(2010b). Copyright 2010 Elsevier).

of counter ions, etc.) and the carbonisation con-ditions (temperature, gas used, etc.) (Table 1). Itshould be noted that conductivity data on the C-PANIs produced are missing in many studies. Nanos-tructured C-PANIs showed increased conductivity bymore than one order of magnitude compared withthe corresponding PANI salt precursors (Mentus etal., 2009; Janoševic et al., 2011, 2012). The high-est conductivity of 0.83 S cm−1 was exhibited by C-PANI produced by the carbonisation of PANI·SSAnanorods/nanotubes (Janoševic et al., 2011). Takinginto account the changes in conductivity of PANIsalt nanotubes during carbonisation, as observed byLanger and Golczak (2007) and Yin et al. (2010b)(Fig. 13), a comparative study of the structure andproperties of the self-assembled PANI salt nanotubesand the products of their carbonisation (Mentus etal., 2009) indicated the occurrence of the followingstructural transformation pattern during the carbon-isation process of PANI emeraldine salt: conduct-ing paramagnetic PANI emeraldine salt nanotubes →non-conducting (de-doped) thermally degraded PANI-

xiv G. Ciric-Marjanovic et al./Chemical Papers

Table 1. Data on nitrogen content (determined by elemental analysis), electrical conductivity (σ), specific surface area (SBET)determined according to the Brunauer–Emmet–Teller (BET) method, total pore volume (Vtot), and micropore volume(Vmic) of C-PANIs produced by carbonisation of the given precursor at a specified temperatures (T)

T N σ SBET Vtot VmicPrecursor Reference

◦C mass % S cm−1 m2 g−1 cm3 g−1 cm3 g−1

PANI base 14.6 2.0 × 10−13 – – – Trchová et al. (2006)300 PANI base 13.8 1.8 × 10−11 – – – Rozlívková et al. (2011)

PANI citrate 12.1 ≈ 1.0 × 10−9 – – – Yin et al. (2010b)

PANI base 16.9 8.5 × 10−14 – – – Trchová et al. (2006)400 PANI base 14.4 2.5 × 10−11 – – – Rozlívková et al. (2011)

PANI citrate 12.9 ≈ 4.2 × 10−10 – – – Yin et al. (2010b)

PANI base 14.9 9.2 × 10−11 – – – Rozlívková et al. (2011)500 PANI citrate 13.1 ≈ 2.2 × 10−9 – – – Yin et al. (2010b)

PANI salt – 1.3 × 10−11 – – – Langer and Golczak (2007)

550 PANI citrate 12.6 – – – – Yin et al. (2010b)

PANI base 16.8 3.1 × 10−10 – – – Trchová et al. (2006)

600PANI base 13.9 1.2 × 10−8 – – – Rozlívková et al. (2011)PANI.H2SO4 – – 1166 1.05a – Lei et al. (2009a)PANI citrate 12.1 ≈ 1.1 × 10−7 – – – Yin et al. (2010b)

PANI base 13.3 1.6 × 10−7 – – – Rozlívková et al. (2011)PANI salt – 2287 – – Li et al. (2010d)

700 PANI citrate 9.6 ≈ 3.2 × 10−3 – – – Yin et al. (2010b)PANI salt 16.6 – 516 – – Yuan et al. (2011)PANI.H2SO4 1190 1.09a – Lei et al. (2009a)

PANI base 13.9 6.7 × 10−6 – – – Trchová et al. (2006)PANI base 10.3 8.6 × 10−4 – – – Rozlívková et al. (2011)PANI salt – 2.4 × 10−6 – – – Langer and Golczak (2007)PANI citrate 5.6 ≈ 0.1 – – – Yin et al. (2010b)

800 PANI salt 8.1 – 666 – – Yuan et al. (2011)PANI·SSA 9.9 0.83 317 0.411a 0.128 Janoševic et al. (2011)

0.224b Gavrilov et al. (2012c)PANI·DNSA 9.8 0.35 441 0.209a 0.185 Janoševic et al. (2012)

0.181b Gavrilov et al. (2012c)PANI·H2SO4 8.9 0.7 – – – Mentus et al. (2009)PANI·H2SO4 8.9 0.32 322 0.209b 0.138 Gavrilov et al. (2012c)

830 PANI base 8.7 – 64.3 – – Trchová et al. (2009)8.8 94.2

PANI·HCl – – 2416 1.55 – Chen et al. (2011b)

850PANI·HCl – – 233.5 0.465b 0.012 Kim and Park (2012a)PANI·HCl 1.4 – 1958 1.28b 0.74 Kim and Park (2012b)PANI·H2SO4 961 0.90a Lei et al. (2009a)

900 PANI salt 7.0 – 641 – – Yuan et al. (2011)950 PANI·H2SO4 – 988 1.08a Lei et al. (2009a)1000 PANI base 6.0 7.3 × 10−4 – – – Trchová et al. (2006)

a) Vtot was calculated at a relative pressure of 0.999; b) Vtot was calculated at a relative pressure of 0.98.

NTs → conducting, partially graphitised, oxygen-containing NCNTs.The electrical conductivity of C-PPYs is in the

range of (10−1–103) S cm−1 (Table 2). It is worthnoting that, as the carbonisation temperature was in-creased from 1000◦C to 2400◦C, the conductivity ofC-PPY microtubes was enhanced from 81 S cm−1

(1000◦C), to 197 S cm−1 (2000◦C) and even to 980S cm−1 (2400◦C) (Han et al., 2001a). The conductiv-ity of the C-PPY nanoparticles as prepared was alsodramatically enhanced to 219 S cm−1 and 370 S cm−1

at the carbonisation and graphitisation temperaturesof 1300◦C and 2300◦C, respectively (Li et al., 2010a).As in the literature about C-PANIs, in many works on

G. Ciric-Marjanovic et al./Chemical Papers xv

Table 2. Data on nitrogen content (determined by elemental analysis), electrical conductivity (σ), specific surface area (SBET)determined according to the Brunauer–Emmet–Teller (BET) method, total pore volume (Vtot), and micropore volume(Vmic) of C-PPYs produced by carbonisation of the given precursor at a specified temperatures (T)

T N σ SBET Vtot VmicPrecursor Reference

◦C mass % S cm−1 m2 g−1 cm3 g−1 cm3 g−1

300 PPY·HCl 14.1 – 23 – – Su et al. (2011)

600PPY·HCla 2.5 – 2050 1.03b 0.74 Sevilla et al. (2011a)

PPY·HCl 12.5 – 36 – – Su et al. (2011)

650 PPY·HCla 10.3 4.9 2381 – – Qie et al. (2012)

700PPY·HCla 0.7

2.1– 3480

29402.39b

1.37b1.181.14

Sevilla et al. (2011a)

PPY·H2SO4 11.9 – 176 – – Kuroki et al. (2012)

800PPY·HCla 0.5

0.8– 3450

34102.57b

1.94b1.221.21

Sevilla et al. (2011a)

850PPY·HCla 0.3 3360 2.62b 1.22 Sevilla et al. (2011a)

PPY·HCl – – 1560 1.4 – Yang et al. (2005)

PPY·HCl – – 74.5 – – Li et al. (2009)

PPY·HCl 7.0 89 – – Su et al. (2011)

PPY·HCl 4.6 – – – – Shang et al. (2009)

PPY·HCl – – 402–621 – – Liu et al. (2012)

900 PPY·HCl 4.74.2

0.110.14

11701060

1.30b

1.47b– Fuertes and Centeno (2005)

PPY·HCl 2.0 – 983 0.99 – Kim et al. (2007)

PPY·HCl 3.8 – 718 1.23 – Kim et al. (2008)

PPY·H2SO4 10.3 – 168 – – Kuroki et al. (2012)

PPY·TSA 4 – – – – Dong and Jones (2006)

1000PPY·TSA < 3 – – – – Han et al. (1999)

PPY·TSA – 81 – – – Han et al. (2001a)

PPY·HNO3 – 21 – – – Li et al. (2010a)

1100PPY·HCl 3.1 1180 – – – Liao et al. (2010)

PPY·HCl 5.9 – 20 – – Su et al. (2011)

1300PPY·HCl 4.3 – 12 – – Su et al. (2011)

PPY·HNO3 – 219 – – – Li et al. (2010a)

1600 PPY·TSA – 145 – – – Han et al. (2001a)

2000 PPY·TSA – 197 – – – Han et al. (2001a)

2300 PPY·HNO3 – 370 – – – Li et al. (2010a)

2400 PPY·TSA 980 Han et al. (2001a)

a) After synthesis, the PPY·HCl precursor was mixed with KOH and heated to the specified temperature, thus chemical activationwas performed simultaneously with carbonisation; b) Vtot was calculated at a relative pressure of 0.999.

C-PPYs their conductivities were not measured.

Elemental composition

The bulk elemental composition of C-PANIs andC-PPYs depends significantly on the PANI or PPY

precursor used and the carbonisation method applied.The N content in the C-PANIs studied is in the rangeof 1.4–16.9 mass % (Table 1), while the N contentin C-PPYs is in the range of 0.3–14.1 mass % (Ta-ble 2). In the case of carbonisation of various nanos-tructured PANI salts, the bulk concentration of het-

xvi G. Ciric-Marjanovic et al./Chemical Papers

Fig. 14. Fitted high-resolution XPS N1s and O1s spectra of carbonised nanostructured PANI·SSA (C-nanoPANI–SSA), carbonisedPANI sulphate/hydrogensulphate (C-nanoPANI), and carbonised PANI·DNSA (C-nanoPANI–DNSA). (Reprinted withpermission from Gavrilov et al. (2012c). Copyright 2012 Elsevier).

eroatoms (N, O), determined by elemental microanal-ysis, is found to be higher than the surface concentra-tion of heteroatoms (determined by XPS), while thebulk carbon content was significantly lower than thesurface carbon content (Gavrilov et al., 2012c). Theseresults indicated that the carbonisation of the sur-faces of all the nanostructured PANI precursors used(containing nanorods, nanotubes and/or nanosheets)was much more efficient than their bulk carbonisa-tion. The heterogeneous core/shell structure of C-PANIs (Gavrilov et al., 2012c; Janoševic et al., 2012)could be a general phenomenon, since many inves-tigators omitted to compare the elemental compo-sition obtained by ordinary elemental analysis andby XPS. Low hydrogen content in C-PANIs is anindication of the efficient condensation of benzenerings with N- and O-containing heterocyclic rings(Mentus et al., 2009; Janoševic et al., 2011, 2012).The change in elemental content of C-PANI withthe change in the carbonisation temperature wasstudied by several research groups (Trchová et al.,2006; Rozlívková et al., 2011; Yin et al., 2010b);it was observed that, in general, the nitrogen con-tent first increased at temperatures up to 500◦C, andthen decreased with any further increase in tempera-ture.

XPS spectroscopy

XPS, as a surface characterisation technique, iscommonly used to identify the surface elemental com-positions and the chemical states of carbon, nitrogenand oxygen in C-PANIs and C-PPYs (Fig. 14). Thesurface O-, N-, and C-containing functional groups inC-PANIs and C-PPYs were identified by deconvolu-tion of the O1s, N1s, and C1s XPS signals. Greatestattention was paid to N-functionalities (Han et al.,2008; Wu et al., 2008b, 2008c; Kim et al., 2009; Muraiet al., 2009; Hsu et al., 2010; Yang et al., 2010; Zhouet al., 2010; Chen et al., 2011a, 2012b; Jeon et al.,2011; Kuo & Hsu, 2011; Ma et al., 2011; Sevilla et al.,2011b; Su et al., 2011; Hsu & Kuo, 2012; Janoševicet al., 2012; Kim & Park, 2012a, 2012b; Kuo et al.,2012; Kuroki et al., 2012; Qie et al., 2012) (Fig. 15).The investigations were focused on the ratio of pyri-dinic nitrogen to pyrrolic, quaternary and N-oxide ni-trogen (Figs. 1 and 15). The O-functionalities (Jin etal., 2010), such as the C——O quinone type groups, C—OH phenol groups or ether C—O—C groups,—COOHgroups, and C-functionalities (Yang et al., 2005), suchas C——C, C—N, C——N, COOH, and COOR, were sel-dom investigated individually; instead, comparativestudies of N- and O-functionalities (Lei et al., 2009b;

G. Ciric-Marjanovic et al./Chemical Papers xvii

Fig. 15. Proposed N-containing C-PANI structural segments: V and VII (Langer & Golczak, 2007), VI and XI (Trchová et al.,2006; Rozlívková et al., 2011; Morávková et al, 2012b), VIII and X (Mentus et al., 2009), IX (Li et al., 2011), and XII(Ho et al., 2009).

Gavrilov et al., 2012c), N- and C-functionalities (Linet al., 2008; Lei et al., 2009a; Lezanska et al., 2010;Su et al., 2010; Xiang et al., 2011b; Gavrilov et al.,2012b), and N-, O-, and C-functionalities (Choi et al.,2007; Li et al., 2010c, 2011; Guo et al., 2011; Xiang etal., 2011a, 2011c, 2011d) were performed. The relativecontent of individual N-, C-, and O-containing func-tional groups was calculated (Gavrilov et al., 2012b,2012c; Janoševic et al., 2012). It was noted that, be-sides the ordinary pyridinic nitrogen, the phenazine

type of pyridinic nitrogen (Fig. 15), identified by itsN1s XPS peak at binding energy of 398.7 eV, may alsobe perceived in N-containing carbon materials derivedfrom PANI (Gavrilov et al., 2012c).The subtle differences observed in the surface el-

emental compositions and chemical states of carbon,nitrogen and oxygen were found to be important forthe performance of these C-PANI materials in variousapplications, such as charge storage (Gavrilov et al.,2012c) and electrocatalysis (Gavrilov et al., 2012b).

xviii G. Ciric-Marjanovic et al./Chemical Papers

Fig. 16. Raman spectra of PANI·DNSA with morphology ofnanorods (PANI·DNSA-NR) and of a product of itscarbonisation (C-PANI·DNSA-NR). (Reprinted withpermission from Janoševic et al. (2012). Copyright2012 Elsevier).

Raman spectroscopy

The main features in the Raman spectra of car-bon materials are the so-called G band (the graphiticband, due to the stretching vibration of any pair ofsp2 sites) and the D band (the disorder-induced band,i.e., the defect-induced band, due to the breathing vi-brations of sp2 sites in six-fold aromatic rings). Whileperfectly ordered graphite exhibits only a single Ra-man (G) band at about 1580 cm−1, the presence ofstructural defects and the reduction in symmetry indisordered carbon materials lead to the broadeningand shift of the G band towards a higher wavenum-ber, as well as to the appearance of the D band ataround 1350 cm−1. The complex structure of the Ra-man spectra of both PANI and PPY is lost upon car-bonisation. The Raman spectra of C-PANIs preparedby the carbonisation of various PANI precursors attemperatures in the range of 600–1000◦C, measuredwith the excitation lines in the visible range (com-monly 488 nm, 514 nm, 532 nm, 633 nm, and 785 nm),are characterised by two broad bands with maxima at1588–1608 cm−1 (the graphitic, G band) and 1340–1366 cm−1 (the disorder-induced D band) (Trchováet al., 2006, 2009; Mentus et al., 2009; Stejskal et al.,2010; Gavrilov et al., 2011b; Rozlívková et al., 2011;Janoševic et al., 2011, 2012) (Fig. 16).The Raman spectra of C-PPYs are similar to those

of C-PANIs, and contain two main bands at around1350 cm−1 (D band) and 1580 cm−1 (G band), at-tributed to the disordered structure and graphite-likestructure of carbon materials, respectively (Fuertes& Centeno, 2005; Han et al., 1999). The band po-sition depends on the type of PANI and PPY pre-cursor (i.e., salt/base, granular/nanostructured, pow-

der/film), carbonisation conditions and the excitationwavelength used for the recording of Raman spectra.In the Raman spectra of various carbonised PANImaterials, the intensity of D band, ID, was found tobe significantly higher than the intensity of G band,IG, and the G band was up-shifted relative to itsposition for perfectly ordered graphite (Trchová etal., 2006, 2009; Mentus et al., 2009; Stejskal et al.,2010; Gavrilov et al., 2011b; Rozlivková et al., 2011;Janoševic et al., 2011, 2012). These spectral featuresindicated significant disorder in these materials, dueto the incorporation of nitrogen (sp3, sp2, and/or sphybridised) and oxygen (sp3 and/or sp2 hybridised)atoms, as well as due to the presence of sp3 and/or sphybridised carbon atoms in the sp2 graphite-type net-work structure of nanostructured C-PANIs (Mentuset al., 2009; Janoševic et al., 2011, 2012). The widthof the Raman bands is also a very important featurein the description of carbon materials. Due to the in-creased disordering, the G and D bands of C-PANIsand C-PPYs are generally broad, in contrast with thesharp bands in the Raman spectra of graphites orgraphenes.As with other disordered carbon materials, the D

band in the Raman spectra of C-PANIs was shown tohave a strong resonant character, as its position andintensity depend on the excitation wavelength used.For the C-PANI produced from a granular PANI base(prepared by the deprotonation of PANI hydrochlo-ride) by carbonisation at 1000◦C, it was found thatthe D band was drastically shifted from 1308 cm−1

for the 1064 nm excitation line to 1366 cm−1 for the488 nm excitation line (Trchová et al., 2006). The Gband had the same position of 1608 cm−1 for bothexcitation lines. The Raman spectra of the C-PANIproduced from a granular PANI base, recorded withthree different laser excitation lines, showed that theintensity of the D band, relative to the G band, in-creased when changing from the 514 nm, 633 nm linesto the 785 nm laser excitation line (Rozlivková et al.,2011).

FTIR spectroscopy

It is a characteristic of carbon materials that theRaman-active D- and G bands are inactive in theirFTIR spectra. However, in disordered carbon mate-rials such as N-containing carbon materials, the D-and G bands become IR-active because of symmetry-breaking of the carbon network. For that reason, twocharacteristic broad G and D absorption bands arepresent in the FTIR spectra of C-PANIs and C-PPYs,reflecting the presence of nitrogen, oxygen and hy-drogen in their structures, in addition to carbon—carbon bonding. The FTIR spectra of C-PANIs arecomposed of two dominant broad bands with max-ima observed in the range of ≈ 1560–1619 cm−1 (Gband) and 1240–1314 cm−1 (D band), Fig. 17, whose

G. Ciric-Marjanovic et al./Chemical Papers xix

Fig. 17. FTIR spectra of nanotubular PANI (NT-1) and ofa product obtained by its carbonisation (N-CNT-1).PANI-NTs (NT-1) were produced by oxidation of ani-line with APS in an aqueous solution of succinic acidand deprotonated. (Reprinted with permission fromTrchová et al. (2009). Copyright 2009 Elsevier).

positions depend on the type of the PANI precursor(Langer & Golczak, 2007; Trchová et al., 2009; Mentuset al., 2009; Janoševic et al., 2011, 2012; Morávková etal., 2012b). A broad absorption over the whole rangeof 400–4000 cm−1, which was assigned to the excita-tion of free conducting electrons, was also observed(Langer & Golczak, 2007; Trchová et al., 2009; Men-tus et al., 2009; Janoševic et al., 2011, 2012). Thestructural changes in the granular PANI base and thePANI hydrochloride films during carbonisation havebeen studied by FTIR spectroscopy (Trchová et al.,2006; Morávková et al., 2012b).

NMR spectroscopy

A new analytical method for characterising the ni-trogen sites in N-containing carbon catalysts, synthe-sised by the carbonisation of N-containing conduct-ing polymers such as PPY, was proposed by employ-ing 15N solid-state NMR (Kuroki et al., 2012). 15N-labelled polypyrrole was prepared as a precursor ofN-containing carbon catalysts and it was pyrolysedat several different temperatures in a nitrogen at-mosphere. 15N solid-state NMR spectra showed thatthe pyrolysed PPY contained pyridinic, quaternary,pyrrolic nitrogen atoms at the edges or at defects inthe graphitic sheets.

EPR spectroscopy

C-PANI-NTs showed the EPR signal with a peakarea four orders of magnitude smaller than theEPR signal of the starting nanotubular PANI sul-phate/hydrogensulphate salt (produced by the poly-merisation of aniline in water), while the g value re-

Fig. 18. XRD pattern of the C-PANI·DNSA-NR, obtainedby carbonisation of PANI·DNSA nanorods (PANI·DNSA-NR). (Reprinted with permission from Janoše-vic et al. (2012). Copyright 2012 Elsevier).

mained unchanged, at 2.003 (Mentus et al., 2009).These results indicated the presence of a significantlylower concentration of paramagnetic centres in C-PANI. Line-width decreased upon carbonisation from2.0 G for starting PANI to 1.8 G for C-PANI-NTs. Theevolution of EPR spectra with the increase in temper-ature during the carbonisation of nanotubular PANIwas studied by Langer and Golczak (2007). From theEPR spectra of C-PPYs measured at 150 K, the gvalue of the main signal at 3409 G was determined as2.00 (Kuroki et al., 2012).

X-ray diffraction (XRD) analysis

N-containing carbon materials, produced by thecarbonisation of PANI and PPY precursors, exhibitedthe XRD patterns consisting of two dominant diffrac-tion peaks at 2θ around 22–26◦ and 44◦, which areclose to the reflections of graphitic planes (002) and(101), respectively (Han et al., 1999; Jang & Stucky,2002; Fuertes & Centeno, 2005; Janoševic et al., 2012;Gavrilov et al., 2012b; Cao et al., 2012) (Fig. 18).These peaks may be broad as well as sharp, dependingon the carbonisation conditions and type of PANI andPPY precursor. The prominent broad peak at ≈ 24◦is an indication of the dominant presence of the amor-phous carbon phase (Janoševic et al., 2012; Gavrilov etal., 2012b). In the case of a PANI precursor doped with3,5-dinitrosalicylic acid, the XRD pattern of the cor-responding C-PANI exhibited additional sharp peaksat 43.1◦, 44.0◦, and ≈ 50.2◦, attributed to the lowamount of highly crystalline graphitic phase in thismaterial (Janoševic et al. (2012), Fig. 18). From theposition of the (002) peak, the interlayer distancesd(002) of the graphitic layers in C-PANI and C-PPY

xx G. Ciric-Marjanovic et al./Chemical Papers

were calculated to be 0.37 nm (Cao et al., 2012) and0.336 nm (Fuertes & Centeno, 2005), respectively.Based on the full width at half-maximum of the (002)and (101) diffraction peaks, the c-axis length (Lc)and a-axis length (La) in the graphite lattice of C-PANI were estimated to be 1.27 nm and 2.12 nm, re-spectively (Cao et al., 2012). These XRD results sug-gested that the C-PANI hollow nanowires were com-posed of disordered graphite nanocrystallites with 3–4(1.27/0.37 = 3.4) layer-stacked-graphene sheets (Caoet al., 2012). The degree of graphitisation/crystallinityincreased with the increase in carbonisation temper-ature (Chen et al., 2012b; Han et al., 1999). It wasreported that the amorphous tubular-shaped nanocar-bon, prepared by pyrolysis of the tubular-shaped self-assembled PANI D-camphorsulphonate, crystallised tosome extent by heat treatment at 2600◦C (Kyotani etal., 2008).

Textural properties

The textural properties, e.g., pores structure, pore-size distribution, and specific surface area (Tables 1and 2) of C-PANI and C-PPY may significantly af-fect their performance in applications such as chargestorage, electrocatalysis, or sensing. For example, theappropriate surface texture is important to afford theelectrolyte/analyte easy access to the complete elec-trode material surface. The textural properties aresignificantly influenced by the type of polymer pre-cursor. To determine the textural properties of nanos-tructured C-PANIs, nitrogen sorption measurementswere performed (Trchová et al., 2009; Janoševic etal., 2011, 2012; Gavrilov et al., 2011b, 2012c). Theisotherms were of type I (for C-PANI produced fromPANI·DNSA), typical of microporous materials (Jano-ševic et al., 2012), or a type I which is modified toa type II isotherm at high relative pressure (for C-PANIs produced from PANI·SSA and PANI hydrogen-sulphate/sulphate) (Janoševic et al., 2011, Gavrilov etal., 2012c) (Fig. 19).It was found that the carbonisation of PANI·DNSA

nanorods yields an essentially microporous mate-rial with a small contribution of mesopores, whilecarbonisation of PANI·SSA and PANI hydrogensul-phate/sulphate lead to microporous materials with alarger contribution of mesoporosity than for PANI·DNSA. The most important change in the texturalproperties upon carbonisation was a drastic increasein the micropore volume in C-PANIs by one order ofmagnitude (≈ 0.13–0.19 cm3 g−1) compared to the mi-cropore volume of the starting nanostructured PANImaterials (≈ 0.012–0.013 cm3 g−1) and, consequently,an increase in SBET, also by one order of magni-tude, from 30–34 m2 g−1 to 317–441 m2 g−1 uponPANI carbonisation (Janoševic et al., 2011, 2012).The total pore volume of C-PANIs was also markedlyhigher (≈ 0.2 cm3 g−1) than the total pore volume

Fig. 19. Nitrogen adsorption–desorption isotherms of PANI·DNSA nanorods (PANI·DNSA-NR) and of a productobtained by its carbonisation (C-PANI·DNSA-NR).Empty symbols are used for adsorption, filled sym-bols are used for desorption. (Reprinted with permis-sion from Janoševic et al. (2012). Copyright 2012 El-sevier).

of PANI precursors (≈ 0.1 cm3 g−1) (Janoševic etal., 2012; Gavrilov et al., 2012c). The highest val-ues of the mesopore surface area (50.1 m2 g−1) andmesopore volume (0.076 cm3 g−1) for C-PANI pro-duced from PANI·SSA were found to be importantfactors in the excellent performance of this mate-rial in charge storage (supercapacitors) applications(Gavrilov et al., 2012c) and electrocatalysis of theoxygen reduction reaction (Janoševic et al., 2011,Gavrilov et al., 2012b). The order of increase in mi-cropore volume: V(C-PANI·SSA) < V(C-PANI hydro-gensulphate/sulphate) < V(C-PANI·DNSA) was theopposite to the order of increase in mesopore volumeand mesopore surface: S(C-PANI·DNSA)< S(C-PANIhydrogensulphate/sulphate) < S(C-PANI·SSA), re-flecting the influence of the different molecular andsupra-molecular structure of PANI precursors, espe-cially different types of counter-ions, on the develop-ment of pore structure during the carbonisation pro-cess (Gavrilov et al., 2012c) (Fig. 20).When the mesoporous silica templates were used in

synthesis of the PPY precursor, the C-PPYs producedhad BET surface areas > 1000 m2 g−1 and porositycomposed by two pore systems with sizes centred at ≈3–4 nm and at 10–14 nm (Fuertes & Centeno, 2005).

Applications

Catalysts

In the vapour-phase selective conversion of meth-acrolein (Kim et al., 2007), benzyl alcohol (Kim etal., 2008), and methanol (Kim et al., 2009), thePMo10V2/C–PPY catalyst showed a higher selec-tive conversion of methacrolein, benzyl alcohol, and

G. Ciric-Marjanovic et al./Chemical Papers xxi

Fig. 20. Pore-size distribution curves, dVmic/dD vs. D (up-per plot) and dVmeso/dD vs. D (lower plot), forcarbonised nanostructured PANI·SSA (C-nanoPANI·SSA), carbonised PANI sulphate/hydrogensulphate(C-nanoPANI) and carbonised PANI·DNSA (C-nanoPANI·DNSA); D, Vmic, and Vmeso are pore di-ameter, micropore volume, and mesopore volume, re-spectively. (Reprinted with permission from Gavrilovet al. (2012c). Copyright 2012 Elsevier).

methanol, respectively, than the bulk PMo10V2 cata-lyst (Kim et al., 2007, 2008, 2009). Furthermore, thePMo10V2/C–PPY catalyst showed a higher selectiv-ity for dimethoxymethane (a product formed by bi-functional oxidation–acid–acid catalysis) and a higherselectivity for methylformate (a product formed bybifunctional oxidation–acid–oxidation catalysis) thanthe PMo10V2 catalyst (Kim et al., 2009). It was foundthat the reaction pathway for the selective conversionof methanol to dimethoxymethane over PMo10V2/C–PPY catalyst could be controlled by changing themethanol feed-rate. The Pd/C–PPY–Fe3O4 compos-ite materials showed an excellent catalytic perfor-mance in the reduction of methylene blue with sodiumborohydride as reducing agent (Yao et al., 2012). Thecatalysts could be readily recycled in an external mag-

netic field and re-used without activity loss.

Electrocatalysts

The electrocatalytic activity of carbonised PANInanostructures (C-nanoPANI) towards the oxygen re-duction reaction (ORR), estimated in 0.1 mol dm−3

KOH solution, was significantly improved upon hy-drothermal treatment in 1 mol dm−3 KOH solution(Gavrilov et al., 2011b), i.e., the onset of ORR wasshifted by≈ 70 mV to more positive potentials and thenumber of electrons consumed per O2 molecule wasenhanced in comparison with the original material.The number of electrons involved in ORR dependedon loading; hence, with a loading of 0.5 mg cm−2,for the potentials lower than –0.5 V vs. SCE, thenumber of electrons approached 4. For this mate-rial, the high stability of electrochemical behaviourand resistance to poisoning by ethanol was confirmedby potentiodynamic cycling. The RDE-voltammetricstudy indicated the excellent electrocatalytic activityof C-nanoPANI·SSA in respect of ORR (onset po-tential of –0.15 V vs. SCE at a catalyst loading of250 µg cm−2 and –0.05 V vs. SCE at a catalyst load-ing of 500 µg cm−2) (Janoševic et al., 2011; Gavrilovet al., 2012b), which is significantly higher than thatof conventional vertically aligned CNT and compara-ble with vertically aligned NCNT grown directly on aGC electrode. The interrelation between the electro-catalytic activity and the electrical double layer charg-ing/discharging characteristics of the C-PANI materi-als investigated was revealed (Gavrilov et al., 2012b).The Pt/C–PANI-CNT catalyst, prepared by an-

choring a uniform dispersion of Pt nanoparticles(≈ 1.5–2.0 nm) on the surface of C-PANI-CNT byusing aromatic amine as a stabiliser, has greatly en-hanced catalytic activity towards the ORR, resultingin an enhancement of ≈ 37 % in mass activity com-pared with that of the commercial E-TEK catalyst(Hsu et al., 2010; Kuo et al., 2012). This is explainedby the higher electrochemical active surface area (upto 103.7 m2 g−1) of Pt/C–PANI-CNTs comparedwith the commercial E-TEK catalyst (55.3 m2 g−1)(Kuo et al., 2012). The electrocatalytic activity ofthe PtNPs–C-nanoPANI nanocomposite towards theORR in both alkaline and acidic solutions was stud-ied using a rotating disc technique by Gavrilov etal. (2011b). In acidic media, this electrocatalyst wascompared with both smooth platinum and commer-cial C-supported Pt-based electrocatalysts. Its higherspecific electrocatalytic activity, which amounted to≈ 1 mA cm−2 Pt at 0.8 V vs. RHE, was demonstrated.It was shown recently that the MnO–C-PANI com-

posite catalyst exhibited high electrocatalytic activityand a dominant four-electron oxygen reduction path-way in 0.1 mol dm−3 KOH aqueous solution due tothe synergetic effect between MnO and C-PANI (Tanet al., 2012). The pristine MnO showed little electro-

xxii G. Ciric-Marjanovic et al./Chemical Papers

catalytic ORR activity and C-PANI alone exhibited adominant two-electron process for ORR. The MnO–C-PANI composite catalyst also exhibited superior sta-bility and methanol tolerance over a commercial Pt/Ccatalyst, making this composite a promising cathodecatalyst for alkaline methanol fuel cell applications.C-PANI–MnO–MWCNTs composites were studied byelectrochemical impedance spectroscopy and used ascatalysts for the ORR (Jin et al., 2010). The sam-ple synthesised from MnO2–MWCNT containing 30mass % of MnO2 followed by carbonisation of thePANI coating at 850◦C showed the best electrochem-ical performance.C-PPY–graphene composites exhibited an excel-

lent performance for the ORR in terms of electro-catalytic activity, stability, and resistance towardsmethanol cross-over and CO poisoning, suggestingtheir potential as metal-free electrocatalysts for theORR (Ma et al., 2011). The ORR of 15N-labelled C-PPY is evaluated by rotating disk electrode experi-ments (Kuroki et al., 2012). The iron-free C-PPY sam-ples displayed quite poor catalytic activity towardsORR, whilst the iron-containing C-PPY samples dis-played better oxygen reduction activity. Using prin-cipal component analysis of the XPS and 15N solid-state NMR spectra, it was found that most pyridinic,quaternary, and pyrrolic nitrogen atoms were not re-lated to ORR. However, the samples which containa larger proportion of some particular type of pyri-dinic nitrogen atoms showed a higher activity for theORR. The electrocatalytic activity and stability ofPt/palygorskite–C-PPY (20 mass % of Pt) compos-ite towards ORR were studied by cyclic voltamme-try (CV) and steady-state polarisation measurements(Wang et al., 2011b). The Pt/palygorskite–C-PPY ex-hibited a superior catalytic performance during ORR,surpassing the conventional Pt/C (Vulcan XC-72) cat-alysts. The high electrocatalytic activity and good sta-bility can be attributed to the nitrogen atom incorpo-ration and SiO2 component in palygorskite. Liu et al.(2009) demonstrated that the high volumetric surfacearea of pyrolysed iron-PPY mesoporous spheres wascritical for improving the activity of non-noble metalcatalysts towards the ORR.The RDE-voltammetric study of ORR at the C-

PANI·DNSA-modified GC electrode revealed that C-PANI·DNSA was an excellent candidate for the elec-trochemical generation of hydrogen peroxide (Janoše-vic et al., 2012). The number of electrons consumedper O2 molecule was found to be close to 2 in the en-tire potential window investigated. Due to its high ni-trogen content, particularly the high relative contentsof pyridinic (41 %) and pyrrolic (50 %) nitrogen re-vealed by XPS, C-PANI·DNSA offers higher ORR on-set potential (close to –0.2 V vs. SCE) than commer-cial carbon materials, this being of great importancefor lower energy consumption. ORR performance, ab-solute H2O2 production rate and selectivity can be op-

timised using specified C-PANI·DNSA catalyst load-ing. It was found that, at a C-PANI·DNSA loadingof 250 µg cm−2, the formation rate of hydrogen per-oxide (2e− reduction) relative to the water formationrate (4e− reduction) was ≈ 100 %.An improved performance for methanol oxidation

was achieved on a high-loading Pt catalyst (up to 60mass %) supported by C-PANI (Wu et al., 2008b). Themethanol oxidation reaction (MOR) on Pt/C–PANIwas investigated by cyclic voltammetry and electro-chemical impedance spectroscopy (Lei et al., 2009a).The Pt/C–PANI showed a generally high CO tol-erance and activity comparable with Pt/XC-72 un-der identical conditions. The Pt/C–PANI shells werefound to exhibit a superior catalytic performance inthe electro-oxidation of methanol, surpassing that ofthe conventional Pt/Vulcan XC-72 catalyst (Lei etal., 2009b). The core/shell CNF–C-PANI compositeswere proven to be better supporting materials for thePt nanocatalysts and showed superior performanceas electrocatalyst supports for MOR over the non-carbonised CNF–PANI composites (Zhou et al., 2012).The current density of MOR on the Pt/C–PANI–CNF catalyst was approximately seven times that onthe Pt–PANI–CNF catalyst. An exceptionally durableand highly active Pt electrocatalyst for MOR was pre-pared by embedding Pt nanoparticles within the poresof a C-PANI layer on the surface of carbon nanotubes(Pt/C–PANI–CNT) (Kuo & Hsu, 2011; Hsu & Kuo,2012). The maximum current density (jmax) in theMOR observed for Pt/C–PANI–CNT (13.2 mA cm−2)was by 20 % higher than that of the commercialPt/XC-72 (10.8 mA cm−2) catalyst. In the acceler-ated durability test, the jmax after 2000 cycles forPt/C–PANI–CNT decreased by 48 %, while Pt/XC-72showed a 96 % decrease (Hsu & Kuo, 2012).C-PPY-supported Pt nanoparticles showed a bet-

ter activity for MOR compared with Vulcan XC-72-supported Pt in terms of both mass and surface spe-cific current densities (Choi et al., 2007). The appli-cability of Pt/C–PPY-NTs electrodes in the anodicoxidation of methanol in direct methanol fuel cellswas investigated by Maiyalagan (2008). The Pt/C–PPY-NTs catalyst exhibited a higher catalytic activ-ity than that of carbon-supported Pt electrode andCNT-supported Pt electrodes. Compared with thePt/C–PPY and E-TEK catalysts, Pt/activated C-PPY showed an enhanced mass activity in MOR be-cause of the high dispersion of small Pt nanoparticles,the presence of nitrogen species and the developed mi-croporous structure of activated C-PPY (Su et al.,2010). The surface modification of graphitised carbonblack with C-PPY led to enhancement of the catalyticactivity of the Pt electrocatalysts for MOR (Jeon etal., 2011). The improvement was largely attributed tothe uniform dispersion of the Pt nanoparticles as theC-PPY modification appeared to reduce the agglom-eration of the Pt nanoparticles. The chronoamperome-

G. Ciric-Marjanovic et al./Chemical Papers xxiii

try and the accelerated cycling tests indicated that theC-PPY modification did not improve the long-termstability of the graphitised carbon black support forPt. An enhanced catalytic activity for MOR was ob-tained for the PtRu/C–PANI–carbon black catalyst incomparison with the traditional PtRu/C catalyst (Wuet al., 2008c). The electro-oxidation of liquid methanolon PtRu/C–PPY catalysts was investigated at ambi-ent temperature by cyclic voltammetry, chronoamper-ometry, and electrochemical impedance spectroscopy(Liu et al., 2011). The results showed that the alloycatalyst (Pt1Ru1/C–PPY) possessed the highest cat-alytic activity and better CO tolerance than the otherPtRu and Pt-only catalysts; PtRu nanoparticles on C-PPY support showed a higher catalytic activity andmore stable sustained current than on carbon blackXC-72. Compared with the commercial Alfa AesarPtRu catalyst, Pt1Ru1/C–PPY showed an enhancedand extended catalytic activity in MOR because of thehigh dispersion of small PtRu nanoparticles and thepresence of N species of in the C-PPY support.The high electrocatalytic activity of PtNPs/C–

nanoPANI towards the ethanol oxidation reaction inacidic medium was recently demonstrated (Gavrilovet al., 2011b).

Fuel cells

Zelenay’s group recently described a family of non-precious metal catalysts that approached the perfor-mance of Pt-based systems at a cost sustainable forhigh-power fuel cell applications, possibly includingautomotive power (Wu et al., 2008a, 2009, 2011).The most active materials in the group catalysedthe ORR at potentials within ≈ 60 mV of that de-livered by the state-of-the-art carbon-supported Pt,combining their high activity with remarkable per-formance stability for non-precious metal catalysts(700 h at a fuel cell voltage of 0.4 V) as well asexcellent four-electron selectivity (hydrogen peroxideyield < 1.0 %). The C-PANI–silica-coated 304 stain-less steel is a promising candidate for bipolar plate ma-terials in proton exchange membrane fuel cells (Wanget al., 2011a). The surface of nanostructured C-PANIwas recently modified by a chemical treatment withNaOH, H2O2, and HNO3 at ambient temperature,and the modified C-PANI materials were used as anunconventional support of nanodispersed Pt electro-catalysts, incorporated in a polymer electrolyte mem-brane fuel cell (PEMFC) (Gavrilov et al., 2012a). Thesurface treatment influenced the mean platinum par-ticle diameter and, consequently, the performance ofPEMFC. In comparison with a conventional nanodis-persed Pt/C catalyst in the same cell, these elec-trocatalysts provided up to 34 % higher power den-sity. Apart from surface modification, the particu-lar chemical composition of the nanostructured C-PANI support itself was suggested as being respon-

sible for the PEMFC performance improvement ob-served.

Supercapacitors

Supercapacitors (also known as electrochemical ca-pacitors) have emerged as attractive power sourceswith high energy and power densities and long cyclelife, complementing or replacing batteries in some en-ergy storage fields. Supercapacitors use high-surface-area electrodes and energy storage is based on fastsurface-charge-storage processes, ion adsorption (elec-trochemical double layer capacitors), and rapid sur-face redox reactions (pseudo-capacitors). Porous car-bon materials have been intensively researched aspromising electrode materials for supercapacitors. Toour knowledge, the first study of the electrochemicalcapacitance of carbonised PANI was reported by Shi-raishi and Mamyouda (2008). It was found that theelectrochemical capacitance of the C-PANI in 1.0 MH2SO4 electrolyte depended on the heat-treatment.The PANI carbonised at 800◦C showed good cycleperformance and 157 F g−1 of the gravimetric ca-pacitance, which was lower than that of the origi-nal PANI but comparable with conventional activatedcarbon fibres (Shiraishi & Mamyouda, 2008). Carbonmaterial prepared by the carbonisation of PANI sul-phate/hydrogen sulphate at 800◦C also had a goodelectrochemical performance and its specific capaci-tance value was 153 F g−1 under a current density of0.5 A g−1 (Li et al., 2010b). The specific capacitanceof C-PANI as high as 235 F g−1 was reported by Liet al. (2010c), and the specific capacitance scarcelydecreased at a high current density of 11 A g−1 af-ter 10000 cycles. The submicro-sized rod-shaped acti-vated C-PANI exhibited a high specific capacitanceof 455 F g−1 and remarkable rate capacity due toits high specific surface area (1976 m2 g−1), narrowpore-size distribution (< 3 nm) as well as short dif-fusion length (Yan et al., 2010). PANI carbonisedsynthesised by the nano-sized silica template methodshowed higher specific capacitance (125 F g−1) thancarbonised PANI prepared without silica (4 F g−1)at a scan rate of 0.2 A g−1 (Kim & Park, 2012a). C-PANI activated with K2CO3 showed a superior capac-itive performance (specific capacitance of 210 F g−1)than the non-activated C-PANI (Xiang et al., 2011d).The C-PANI activated with ZnCl2 presented a high-specific gravimetric capacitance of 174 F g−1, withrectangular cyclic voltammetry curves at a scan rateof 2 mV s−1, and it remained at 93 % even at a highscan rate of 50 mV s−1 (Xiang et al., 2011a). The ex-perimental results demonstrated two mechanisms ofenergy storage in C-PANI: double-layer formation andpseudocapacitance (Li et al., 2011). The overall spe-cific capacitance of non-activated C-PANI is mainlyattributed to pseudocapacitance; that of activated C-PANI prepared by physical activation is attributed to

xxiv G. Ciric-Marjanovic et al./Chemical Papers

the synergic effect of pseudocapacitance and double-layer capacitance, while that of activated C-PANI pre-pared by chemical activation is mainly attributed todouble-layer capacitance (Li et al., 2011).The electrochemical measurements conducted by

cyclic voltammetry and galvanostatic charge–dis-charge demonstrated that the specific capacitance ofC-PANI nanowires electrode material attained 327F g−1 at a current density of 0.1 A g−1 (Yuan etal., 2011). The charge storage ability of N-containingnanostructured carbon materials, C-nanoPANI, C-nanoPANI·DNSA, and C-nanoPANI·SSA prepared bythe carbonisation of nanostructured PANI doped withsulphuric acid, DNSA, SSA, respectively, was investi-gated in an alkaline solution (Gavrilov et al., 2012c).It was found that the specific capacitance increasedin the order to the right: C-nanoPANI·DNSA, C-nanoPANI, C-nanoPANI·SSA. The highest capaci-tance, amounting to 410 F g−1 at a scan rate of5 mV s−1, was found for C-nanoPANI·SSA. At a largerate of 10 A g−1, its capacitance displayed a stablevalue close to 200 F g−1 for 5000 cycles. To explain thedifferences observed in charge storage properties, thematerials were characterised by different techniquescapable of ascertaining their morphology, elementalcomposition, nitrogen surface concentration, chemicalstate of nitrogen, pore structure, and electrical con-ductivity. All materials were essentially microporouswith a relatively small fraction of mesopores and dis-played conductivities in the range of 0.32–0.83 S cm−1.The best charge-storage performance, achieved by C-nanoPANI·SSA, was attributed to its highest surfacefraction of nitrogen, the highest surface content ofpyridinic nitrogen groups, and the highest electricalconductivity, as well as to its well-balanced micro- andmesoporosity and highest content of mesopores. It wasfound that the PANI-NTs carbonised at 700◦C exhib-ited a specific capacitance of 163 F g−1 at a currentdensity of 0.1 A g−1 and an excellent rate capabil-ity in KOH solution (Yang et al., 2010). The spe-cific capacitance of the C-PANI-NTs activated withKOH solution (254.6 F g−1) was higher than thatof the as-prepared C-PANI-NTs (218.6 F g−1) (Kim& Park, 2012b). The C-PANI–graphene exhibited anelectrochemical performance superior to that of pris-tine graphene, while the highest specific capacitance(170 F g−1) of the C-graphene was obtained at a scanrate of 0.1 A g−1, as compared with 138 F g−1 forpristine graphene (Kim & Park, 2011). This superiorperformance was attributed to the synergistic effect ofthe porous C-PANI layer and the graphene and pseu-docapacitive effect by the nitrogen groups formed afterPANI carbonisation.It was found that activated C-PPY nanospheres

with a high surface area and N-containing species ex-hibited a much better capacitive performance thanthe PPY nanospheres and non-activated C-PPYnanospheres, as well as commercial carbon blacks

(XC-72 and BP2000) (Su et al., 2011). The activatedC-PPY nanospheres gave a reversible specific capaci-tance of 240 F g−1 for 3000 cycles in aqueous media asa result of their combined advantages of high electro-chemical activity of heteroatoms (N and O) and ac-cessible well-developed porosity, demonstrating theirpromising use in high-energy-density supercapacitors.A high-capacity supercapacitor material based on theN-containing porous CNFs, synthesised by carbonisa-tion of macroscopic-scale CNFs coated with PPY, wasrecently presented (Chen et al., 2012b). The compositeCNF/C-PPY nanofibres exhibited a reversible specificcapacitance of 202.0 F g−1 at a current density of 1.0A g−1 in 6.0 mol L−1 aqueous KOH electrolyte, main-taining a high-class capacitance retention capabilityand a maximum power density of 89.57 kW kg−1.

Rechargeable batteries

Si/C-PANI|Li cells were fabricated using the Si/C-PANI composites and tested using the galvanos-tatic charge–discharge technique (Doh et al., 2006).Si/C-PANI|Li cells had better electrochemical prop-erties than Si|Li cells. Si/C-PANI|Li cells using Si/C-PANI, prepared from undoped PANI, exhibited bet-ter electrochemical properties than Si/C-PANI|Licells prepared from PANI doped with HCl. Thelithium storage performances of activated and non-activated C-PANI have been studied by galvanostaticcharge/discharge (Li et al., 2010d). The C-PANI with-out activation showed a first discharge capacity of729 mA h g−1, while the first discharge capacity ofthe C-PANI prepared by H3PO4 activation was 1083mA h g−1 and that of the C-PANI prepared by KOHactivation was as high as 2201 mA h g−1, whose re-versible capacity was 1027 mA h g−1. For the C-PANIprepared by KOH activation, the first coulombic ef-ficiency was just 47 %; however, from the second cy-cle, the coulombic efficiency increased rapidly to above90 %, with the reversible capacity still as high as 747mA h g−1 after 20 cycles. The electrochemical proper-ties of the C-PANI-NTs as anode materials in lithiumion batteries were recently evaluated by Xiang et al.(2011c). At a current density of 100 mA g−1, the ac-tivated C-PANI-NTs showed an enormously high firstdischarge capacity of about 1370 mA h g−1 and acharge capacity of 907 mA h g−1. After 20 cycles,the activated C-PANI-NTs retained a reversible ca-pacity of 728 mA h g−1. The electrochemical prop-erties of the activated microporous C–PANI base asan anode material in a lithium ion secondary batterywere also evaluated (Xiang et al., 2011b). The firstdischarge capacity of the microporous carbon materialwas 1108 mA h g−1, whose first charge capacity was624 mA h g−1, with a coulombic efficiency of 56.3 %.After 20 cycles, the microporous C-PANI retained areversible capacity of 603 mA h g−1 at a current den-sity of 100 mA g−1.

G. Ciric-Marjanovic et al./Chemical Papers xxv

Fig. 21. Schematic representation of electron transmissionof Li+ ion storage in carbonised nanofibre webs.(Reprinted with permission from Qie et al. (2012).Copyright 2012 Wiley).

The electrochemical properties of the turbostraticC-PPY nanospheres as anode materials in lithium-ionbatteries were evaluated (Wang et al., 2008a). TheC-PPY nanospheres displayed a higher specific capac-ity than the carbon spheres derived from sucrose anda higher rate capability than commercial mesophasecarbon microbeads. Owing to the high porosity andconducting one-dimensional network, porous C-PPYnanofibres showed enhanced lithium-ion storage prop-erties when used as the anode material in lithium-ion batteries (Li et al., 2009). The reversible specificcapacity of the CNFs at a 0.5 C rate was ≈ 400mA h g−1. Moreover, C-PPY nanofibres exhibited aconsiderably higher specific capacity even at a highcharge–discharge current; i.e., the reversible capaci-ties were around 250 mA h g−1 and 194 mA h g−1 atrates of 10 C and 20 C, respectively. C-PPY nanofi-bre webs (C-PPY-NFWs) with high surface areas, ac-tivated with KOH, exhibited an extremely high re-versible capacity of 943 mA h g−1 at a current den-sity of 2 A g−1 even after 600 cycles, due to theirporous nanostructure and high nitrogen content (Qieet al., 2012). The results recorded by Qie et al. (2012)showed that the C-PPY-NFWs (Fig. 21) are promis-ing anode materials for the next-generation lithiumion batteries with high energy and power density. Car-bonised polyacrylonitrile–PPY composite nanofibreswere used as anodes for rechargeable lithium-ion bat-teries without adding any polymer binder or conduc-tive material; they displayed high reversible capacity,improved cycle performance, relatively good rate ca-pability, and clear fibrous morphology, even after 50charge–discharge cycles (Ji et al., 2010).It was recently shown that the LiFePO4–C-PANI

core/shell nanocomposites with low C-PANI shellthicknesses exhibit poor electrochemical performancewhen used in lithium ion batteries, presumably dueto the presence of structural disorders and defectsin the particle surface layers (Jiang & Jiang, 2012).The LiFePO4–C-PANI nanocomposites with higherC-PANI shell thicknesses exhibit a significantly im-proved electrochemical performance in lithium ion

batteries (Jiang & Jiang, 2012), since an increasein C-PANI shell thickness can remove the structuraldisorders and defects. It is important to note thatan uncontrollable increase in C-PANI shell thicknesswould lead to a decrease in the charge–discharge ca-pacity of the LiFePO4–C-PANI nanocomposites, al-though these LiFePO4–C–PANI nanocomposites con-tinue to exhibit high cycling stability. That is be-cause an excess C-PANI shell coating would hin-der penetration of the electrolyte solution into theC-PANI layers and the inward–outward diffusion ofLi+ ions through the C-PANI layers, hence decreas-ing the charge–discharge capacity of the LiFePO4–C-PANI nanocomposites. The optimised LiFePO4–C-PANI cathode material exhibited a satisfactory rateand cycle performance, thus demonstrating that it wasquite suitable for power lithium ion batteries (Gu etal., 2012). At rates of 0.1 C, 1 C, 2 C, 5 C, and 10 C,it delivered discharge capacities of 161.1 mA h g−1,152.1 mA h g−1, 147.5 mA h g−1, 128.7 mA h g−1,and 109.6 mA h g−1, respectively, with flat voltageplateaus and excellent cycling stability for charge–discharge behaviour. The Li0.97Na0.03FePO4–C-PANIexhibited the best electrochemical performance out ofthe Na-doped LiFePO4–C-PANI composites, with aninitial special discharge capacity of 158 mA h g−1 at0.1 C (Yin et al., 2010a).The Si-CNT–C-PPY microcapsules, having inter-

nal free space generated from a sol–gel silica–polymernetwork for accommodating volume expansion–shrink-age of silicon nanoparticles during the lithium ioncharge–discharge process, were successfully incorpo-rated as anodes in lithium ion batteries (Bae, 2011).They showed a comparably high reversible capacityand a coulombic efficiency (≈ 80%). The use of silicaas an intermediate layer has improved the capacityretention capability of Si-CNT–C-PPY microcapsulessignificantly. The morphology of Si-CNT–C-PPY mi-crocapsules was retained after 50 cycles. The electro-chemical performance of the SnO2–C-PPY (15.1 %carbon) was investigated by cyclic voltammetry anddischarge–charge cycling on half-cells in the potentialrange of 0.005–2 V vs. Li+ /Li at 25◦C (Mi et al.,2011). Galvanostatic cycling showed a stable and highcharge capacity (598.3 mA h g−1) at a current den-sity of 100 mA g−1 over 50 cycles, with low capacityfading of approximately 0.7 % per cycle. By increas-ing the rate after 5 cycles in steps from 50 mA g−1 to300 mA g−1 up to 30 cycles, a high reversible capac-ity (657.9 mA h g−1) was retained. Highly improvedlithium ion storage properties in terms of capacity,rate capability, and cycling stability may benefit fromboth the buffering action of conductive C-PPY net-works and the size effect of SnO2 nanocrystals (Mi etal., 2011).The C-PANI-NTs used as the anode material for

Na-ion batteries delivered a high reversible capacityof 251 mA h g−1 and 82.2 % capacity retention over

xxvi G. Ciric-Marjanovic et al./Chemical Papers

Fig. 22. Electrochemical characterisation and battery performance of hollow carbon nanowires (HCNWs) as anode material forNa-ion batteries. Left: Cycle performance of HCNW electrode at a current density of 50 mA g−1 (0.2 C). Right: Dischargecapacity of HCNW electrode as a function of charge–discharge cycles at different charge–discharge current densities of50 mA h g−1 (0.2 C), 125 mA h g−1 (0.5 C), 250 mA h g−1 (1 C), and 500 mA h g−1 (2 C), respectively. (Reprintedwith permission from Cao et al. (2012). Copyright 2012 ACS).

400 charge–discharge cycles between 1.2 V and 0.01 V(both vs. Na+/Na) at a constant current of 50 mA g−1

(0.2 C) (Cao et al., 2012) (Fig. 22). Excellent cy-cling stability was also observed at an even highercharge–discharge rate. A high reversible capacity of149 mA h g−1 can also be obtained at a current rate of500 mA g−1 (2 C). The good Na-ion insertion propertywas attributed to the short diffusion distance in the C-PANI-NTs and the large interlayer distance (0.37 nm)between the graphitic sheets, which agrees with theinterlayered distance predicted by theoretical calcula-tions to enable Na-ion insertion in carbon materials.

Sensors

MnO2–C-nanoPANI was examined as an electrodematerial for potential applications in the field of elec-troanalysis (Šljukic et al., 2011). It showed a high elec-trocatalytic activity for the sensing of hydrogen per-oxide in an aqueous media. A micro/nanostructuredMnO2–C-PANI·SSA composite based electrode, pre-pared by using the low-temperature wet impregnationprocedure, was tested for the quantitative simultane-ous determination of Pb2+ and Cd2+ as model ana-lytes by anodic stripping voltammetry (Mališic et al.,2012). The oxidation of the targeted heavy metals atthe investigated composite electrode gave distinctiveand well separated peaks with detection limits of 68nM for Pb2+ and 86 nM for Cd2+ ions.

Field emitters

Carbon-based materials have been of great inter-est due to their potential application in cold cathodesfor field emission displays and other vacuum micro-electronic devices. The electron field emission inves-tigations performed by Lin et al. (2008) showed thatthe turn-on field and effective work function of nanos-tructured C-PANI were 1.7 V µm−1 and 0.010 eV;

these were lower than those of N-containing amor-phous carbon films obtained by other methods. Thefield emission characteristics of C-PPY-NTs were re-cently investigated (Bae & Jang, 2012). C-PPY-NTswere successfully employed as field emitters for displayapplication. The C-PPY-NTs so prepared showed afield enhancement factor of 585 and turn-on voltageof 3.5 V mm−1.

Electrorheological fluids

NCNTs, prepared by the carbonisation of PANI-NTs in vacuum, were shown to possess a good elec-trorheological (ER) performance (Yin et al., 2010b,2011). C-PANI-NTs suspensions possessed a versatileER performance including high ER efficiency, gooddispersion stability, and temperature stability (Yin etal., 2010b). Especially when compared with the corre-sponding granular C-PANI suspensions, the C-PANI-NTs suspensions showed better dispersion stabilityand a higher ER effect. Furthermore, the ER effect ofC-PANI-NTs suspensions could be adjusted by vary-ing heat treatment temperatures and the C-PANI-NTs obtained at around 600◦C exhibited the maxi-mum ER effect. The C-PANI-NTs suspension showedgood temperature stability for its ER properties, al-though its zero-field viscosity decreased at elevatedtemperatures (Yin et al., 2011). The flow curve ofshear stress vs. shear rate also maintained a stablelevel and the critical shear rate shifted towards highvalues as the operating temperature increased. Thedynamic viscoelastic measurement showed that thestorage modulus increased slightly with the increas-ing operating temperature, also confirming the goodtemperature stability of the ER properties of the N-CT suspension. An ER suspension was also preparedby dispersing the graphene-supported C-PANI sheetsin silicone oil and its ER property was investigated byrheological tests under electric fields (Yin et al., 2012).

G. Ciric-Marjanovic et al./Chemical Papers xxvii

The suspension demonstrated a strong ER effect. Itsyield stress and shear stress were about three times aslarge as those of a suspension of pure carbon particlesat equal electric field strengths. The storage modulusof the suspension was also higher than that of a sus-pension of pure carbon particles, indicating strongerER activity. Dielectric measurements indicated thatthe presence of the graphene core increased the polar-isation of graphene-supported C-PANI, thus causingits increased ER activity.

Adsorbents

Considerable research efforts are currently beingdirected towards finding materials that can reversiblystore large amounts of hydrogen. The efficient storageand transportation of hydrogen is crucial for the ex-ploitation of hydrogen as an energy source. Porous ma-terials, especially porous carbon materials, have par-ticular potential as hydrogen adsorbents. Activatedrectangular PANI-based carbon tubes are promisinghydrogen adsorbents (Chen et al., 2011b). Hydrogenuptake measurements showed that the highest hydro-gen adsorption reached 5.2 mass % at 5 MPa and77 K and 0.62 mass % at 7.5 MPa and 293 K, respec-tively. Notably, the large pore volume can contribute2.8 mass % to the total hydrogen storage, which ap-proached 8.0 mass % at 5 MPa and 77 K. Chen etal. (2012a) also found that hydrogen adsorption of C-PANI–Fe composites increased from 5.3 mass % to6.2 mass % at 77 K and 5 MPa and 0.6 mass % to0.85 mass % at 293 K and 8 MPa with the increasingFe content. The large specific surface area and highpore volume improved the original hydrogen adsorp-tion heat up to 7.2 kJ mol−1. Carbon materials withultrahigh surface area, obtained via chemical activa-tion of C-PPY with KOH, achieved an excellent hy-drogen storage capacity of up to 7.03 mass % at 77 Kand 2 MPa, which is the highest ever reported for one-step activated carbon materials and amongst the bestfor any porous material (Sevilla et al., 2011a).The mitigation of CO2 emissions has attracted con-

siderable attention due to the fact that this gas isthe main anthropogenic contributor to climate change.Among the different strategies for CO2 abatement,much effort has been devoted to its capture andstorage. Highly porous activated C-PPYs were in-vestigated as sorbents for CO2 capture (Sevilla etal., 2011b). A very high CO2 adsorption uptake of6.2 mmol g−1 (0◦C) was achieved for porous carbonmaterials prepared with KOH : PPy = 2 and 600◦C(1700 m2 g−1, pore size ≈ 1 nm and 10.1 mass % ofN). Furthermore, it was observed that these porousC-PPYs exhibited high CO2 adsorption rates, a goodselectivity for CO2–N2 separation and could be easilyregenerated.It was shown that the urchin-like C-PANI–α-

Fe/γ-Fe2O3 spheres might be used as an adsorbent

for the removal of dyes in wastewaters (Zhu et al.,2009). It was recently found that the hollow C-PANI-lignosulphonate nanospheres could be used as adsor-bents of papain (Lu et al., 2011). The papain adsorp-tion capacity for the C-PANI–lignosulphonate spheresprepared at 1200◦C was up to 1161 mg g−1 at an ini-tial papain concentration of 10 mg mL−1 at 25◦C.

Carbon membranes

Electrically conducting polymers are generally con-sidered as unsuitable precursors for the synthesis ofcarbon membranes because defects always emerge inthe carbon matrices generated from the pyrolysis ofthese polymers. However, Chen et al. (2011a) reportedthat the grafting of dodecylbenzene sulphonic acid(DBSA) chains to the conjugated backbone of PPYcould effectively halt mudcracks from developing inthe carbon matrix. The DBSA side chains impedestrong association of the conjugated PPY molecu-lar segments, since the root cause of mudcracks isthe stacking of PPY segments. A uniform, meso-porous and microcrack-free carbon membrane (3–5µm thick) was prepared on a porous ceramic substrateby means of solution casting and carbonising the castPPY·DBSA layer (Chen et al., 2011a) (Fig. 23). Itwas verified that the solvent used to formulate thePPY·DBSA solution and the final carbonisation tem-perature had significant impacts on the porous struc-ture of the carbon membrane.

Conclusions and outlook

Carbonisation of granular PANI and PPY as wellas their micro- and nanostructures in both salt andbase forms is an elegant way to fabricate N-containingcarbon materials with different (i) morphology, (ii)textural characteristics, (iii) physical properties, (iv)amount of incorporated nitrogen, and (v) types of N-containing functional groups. The properties of theresulting material are determined by the character-istics of the polymer precursor and the conditionsduring the carbonisation process. Current research isdirected towards the development of new advancedC-PANI and C-PPY materials with desired proper-ties and versatile applicability. To date, extensive ap-plications of PANI/PPY-derived N-containing carbonmaterials were reported in the fields of catalysis, en-ergy conversion (electrocatalysis, supercapacitors, fuelcells, and rechargeable batteries), and analytics, aswell as in many other areas such as the fabricationof field emitters, electrorheological fluids, adsorbents,and carbon membranes.Nevertheless, the basic principles regarding inter-

dependence between the properties of the PANI/PPYprecursor, specific carbonisation conditions and theproperties of the resulting carbon material are yetto be fully understood. With greater understanding

xxviii G. Ciric-Marjanovic et al./Chemical Papers

Fig. 23. FESEM micrograph (cross-section) of 3rd layer of carbon membrane derived from PPY which contain dodecylbenzenesulphonic acid as side-chain groups (left). (Reprinted with permission from Chen et al. (2011a). Copyright 2011 Elsevier).

of the process of PANI/PPY carbonisation, it willbe possible to produce advanced N-containing carbonmaterials with pre-defined properties for specific ap-plications. There also remains the possibility of de-signing different model systems of PANI/PPY-derivedN-containing carbon materials using the approach de-scribed above. If accomplished, many important ques-tions regarding the roles of the textural characteris-tics and physicochemical properties of PANI/PPY-based carbon materials, as well as their relationshipwith materials performance, could be answered. Withthese goals ahead, a crucial task for researchers in thefield is the accumulation of fundamental knowledgeregarding the C-PANI/C-PPY structure vs. physico-chemical properties vs. material performance relation-ships, which will require innovative approaches whenit comes to the synthesis of new advanced C-PANI/C-PPY-based materials and their detailed characterisa-tion.

Acknowledgements. The authors wish to thank the Ministryof Education and Science of the Republic of Serbia (OI 172043and III45014) for its financial support. Support received fromCOST (European Cooperation in Science and Technology)within the framework of ESNAM (European Scientific Networkfor Artificial Muscles)-COST Action MP1003- is gratefully ac-knowledged.

References

Bae, J. (2011). Fabrication of carbon microcapsules contain-ing silicon nanoparticles–carbon nanotubes nanocompos-ite by sol–gel method for anode in lithium ion battery.Journal of Solid State Chemistry, 184, 1749–1755. DOI:10.1016/j.jssc.2011.05.012.

Bae, J., & Jang, J. (2012). Fabrication of carbon nanotubes fromconducting polymer precursor as field emitter. Journal ofIndustrial and Engineering Chemistry, 18, 1921–1924. DOI:10.1016/j.jiec.2012.05.004.

Baranauskas, V., Ceragioli, H. J., Peterlevitz, A. C., & Quispe,J. C. R. (2007). Properties of carbon nanostructures preparedby polyaniline carbonization. Journal of Physics: Conference

Series, 61, 71–74. DOI: 10.1088/1742-6596/61/1/015.Cao, Y. L., Xiao, L. F., Sushko, M. L., Wang, W., Schwenzer,B., Xiao, J., Nie, Z. M., Saraf, L. V., Yang, Z. G., & Liu,J. (2012). Sodium ion insertion in hollow carbon nanowiresfor battery applications. Nano Letters, 12, 3783–3787. DOI:10.1021/nl3016957.

Chen, X. W., Hong, L., Chen, X. L., Yeong, W. H. A., & Chan,W. K. I. (2011a). Aliphatic chain grafted polypyrrole as aprecursor of carbon membrane. Journal of Membrane Sci-ence, 379, 353–360. DOI: 10.1016/j.memsci.2011.06.007.

Chen, Y. Z., Zhu, H. Y., & Liu, Y. N. (2011b). Prepa-ration of activated rectangular polyaniline-based carbontubes and their application in hydrogen adsorption. Interna-tional Journal of Hydrogen Energy, 36, 11738–11745. DOI:10.1016/j.ijhydene.2011.01.119.

Chen, Y. Z., Cao, X. Z., Zhu, H. Y., & Liu, Y. N. (2012a). Prepa-ration of a porous carbon from ferrocene-loaded polyanilineand its use in hydrogen adsorption. International Journal ofHydrogen Energy, 37, 7629–7637. DOI: 10.1016/j.ijhydene.2011.09.107.

Chen, L. F., Zhang, X. D., Liang, H. W., Kong, M. G., Guan,Q. F., Chen, P., Wu, Z. Y., & Yu, S. H. (2012b). Synthesisof nitrogen-doped porous carbon nanofibers as an efficientelectrode material for supercapacitors. ACS Nano, 6, 7092–7102. DOI: 10.1021/nn302147s.

Choi, B., Yoon, H., Park, I. S., Jang, J., & Sung, Y. E.(2007). Highly dispersed Pt nanoparticles on nitrogen-dopedmagnetic carbon nanoparticles and their enhanced activ-ity for methanol oxidation. Carbon, 45, 2496–2501. DOI:10.1016/j.carbon.2007.08.028.

Ciric-Marjanovic, G. (2010). Polyaniline nanostructures. In A.Eftekhari (Ed.), Nanostructured conductive polymers (pp.19–98). London, UK: Wiley. DOI: 10.1002/9780470661338.ch2.

Ciric-Marjanovic, G., Dragičevic, L., Milojevic, M., Mojovic,M., Mentus, S., Dojčinovic, B., Marjanovic, B., & Stej-skal, J. (2009). Synthesis and characterization of self-assembled polyaniline nanotubes/silica nanocomposites. TheJournal of Physical Chemistry B, 113, 7116–7127. DOI:10.1021/jp900096b.

Dai, X. Y., Zhang, X., Meng, Y. F., & Shen, P. K. (2011).Preparation of hollow carbon spheres by carbonization ofpolystyrene/polyaniline core-shell polymer particles. NewCarbon Materials, 26, 389–395. DOI: 10.1016/s1872-5805(11)60089-9.

G. Ciric-Marjanovic et al./Chemical Papers xxix

Doh, C. H., Kim, S. I., Jeong, K. Y., Jin, B. S., An, K. H., Min,B. C., Moon, S. I., & Yun, M. S. (2006). Synthesis of silicon-carbon by polyaniline coating and electrochemical propertiesof the Si-C|Li cell. Bulletin of the Korean Chemical Society,27, 1175–1180. DOI: 10.5012/bkcs.2006.27.8.1175.

Dong, H., & Jones, W. E. (2006). Preparation of submicronpolypyrrole/poly(methyl methacrylate) coaxial fibers andconversion to polypyrrole tubes and carbon tubes. Langmuir,22, 11384–11387. DOI: 10.1021/la061399t.

Dupuis, A. C. (2005). The catalyst in the CCVD of carbonnanotubes—a review. Progress in Material Science, 50, 929–961. DOI: 10.1016/j.pmatsci.2005.04.003.

Fuertes, A. B., & Centeno, T. A. (2005). Mesoporous carbonswith graphitic structures fabricated by using porous silicamaterials as templates and iron-impregnated polypyrrole asprecursor. Journal of Materials Chemistry, 15, 1079–1083.DOI: 10.1039/b416007j.

Ganesan, Y., Peng, C., Lu, Y., Ci, L., Srivastava, A., Ajayan,P. M., & Lou, J. (2010). Effect of nitrogen doping on themechanical properties of carbon nanotubes. ACS Nano, 4,7637–7643. DOI: 10.1021/nn102372w.

Gavrilov, N., Dašic-Tomic, M., Pašti, I., Ciric-Marjanovic, G., &Mentus, S. (2011a). Carbonized polyaniline nanotubes/nano-sheets-supported Pt nanoparticles: Synthesis, characteriza-tion and electrocatalysis. Materials Letters, 65, 962–965.DOI: 10.1016/j.matlet.2010.12.044.

Gavrilov, N., Vujkovic, M., Pašti, I. A., Ciric-Marjanovic, G.,& Mentus, S. V. (2011b). Enhancement of electrocatalyticproperties of carbonized polyaniline nanoparticles upon ahydrothermal treatment in alkaline medium. Electrochim-ica Acta, 56, 9197–9202. DOI: 10.1016/j.electacta.2011.07.134.

Gavrilov, N. M., Pašti, I. A., Ciric-Marjanovic, G., Nikolic,V. M., Kaninski, M. P. M., Miljanic, S. S., & Mentus, S.V. (2012a). Nanodispersed platinum on chemically treatednanostructured carbonized polyaniline as a new PEMFC cat-alysts. International Journal of Electrochemical Science, 7,6666–6676.

Gavrilov, N., Pašti, I. A., Mitric, M., Travas-Sejdic, J., Ciric-Marjanovic, G., & Mentus, S. (2012b). Electrocatalysis ofoxygen reduction reaction on polyaniline-derived N-dopedcarbon nanoparticle surfaces in alkaline media. Journal ofPower Sources, 220, 306–316. DOI: 10.1016/j.jpowsour.2012.07.119.

Gavrilov, N., Pašti, I. A., Vujkovic, M., Travas-Sejdic, J., Ciric-Marjanovic, G., & Mentus, S. V. (2012c). High-performancecharge storage by N-containing nanostructured carbon de-rived from polyaniline. Carbon, 50, 3915–3927. DOI: 10.1016/j.carbon.2012.04.045.

Geim, A. K., & Novoselov, K. S. (2007). The rise of graphene.Nature Materials, 6, 183–191. DOI: 10.1038/nmat1849.

Gong, K. P., Du, F., Xia, Z. H., Durstock, M., & Dai, L. M.(2009). Nitrogen-doped carbon nanotube arrays with highelectrocatalytic activity for oxygen reduction. Science, 323,760–764. DOI: 10.1126/science.1168049.

Gu, N. Y., He, X. H., & Li, Y. (2012). LiFePO4@C cathode ma-terials synthesized from FePO4@PAn composites. MaterialsLetters, 81, 115–118. DOI: 10.1016/j.matlet.2012.05.003.

Guo, Y. X., He, J. P., Wang, T., Xue, H. R., Hu, Y. Y., Li,G. X., Tang, J., & Sun, X. (2011). Enhanced electrocatalyticactivity of platinum supported on nitrogen modified orderedmesoporous carbon. Journal of Power Sources, 196, 9299–9307. DOI: 10.1016/j.jpowsour.2011.07.073.

Han, C. C., Lee, J. T., Yang, R. W., Chang, H., & Han, C. H.(1999). A new and easy method for making well-organizedmicrometer-sized carbon tubes and their regularly assem-bled structures. Chemistry of Materials, 11, 1806–1813. DOI:10.1021/cm990032p.

Han, C. C., Lee, J. T., & Chang, H. (2001a). Thermal anneal-ing effects on structure and morphology of micrometer-sizedcarbon tubes. Chemistry of Materials, 13, 4180–4186. DOI:10.1021/cm010333a.

Han, C. C., Lee, J. T., Yang, R. W., & Han, C. H. (2001b). For-mation mechanism of micrometer-sized carbon tubes. Chem-istry of Materials, 13, 2656–2665. DOI: 10.1021/cm010141f.

Han, C. C., Bai, M. Y., Yang, K. F., Lee, Y. S., & Lin, C.W. (2008). A novel method for making highly dispersibleconducting polymer and concentric graphitic carbon nano-spheres based on an undoped and functionalized polyani-line. Journal of Materials Chemistry, 18, 3918–3925. DOI:10.1039/b804131h.

Hellgren, N., Johansson, M. P., Broitman, E., Hultman, L.,& Sundgren, J. E. (1999). Role of nitrogen in the forma-tion of hard and elastic CNx thin films by reactive mag-netron sputtering. Physical Review B, 59, 5162–5169. DOI:10.1103/PhysRevB.59.5162.

Ho, K. S., Han, Y. K., Tuan, Y. T., Huang, Y. J., Wang, Y.Z., Ho, T. H., Hsieh, T. H., Lin, J. J., & Lin, S. C. (2009).Formation and degradation mechanism of a novel nanofi-brous polyaniline. Synthetic Metals, 159, 1202–1209. DOI:10.1016/j.synthmet.2009.02.047.

Hsu, C. H., Wu, H. M., & Kuo, P. L. (2010). Excellent per-formance of Pt0 on high nitrogen-containing carbon nano-tubes using aniline as nitrogen/carbon source, dispersant andstabilizer. Chemical Communications, 46, 7628–7630. DOI:10.1039/c0cc02018d.

Hsu, C. H., & Kuo, P. L. (2012). The use of carbon nanotubescoated with a porous nitrogen-doped carbon layer with em-bedded Pt for the methanol oxidation reaction. Journal ofPower Sources, 198, 83–89. DOI: 10.1016/j.jpowsour.2011.10.012.

Hu, J. T., Yang, P. D., & Lieber, C. M. (1998). Nitrogen-driven sp3 to sp2 transformation in carbon nitride materials.Physical Review B, 57, R3185–R3188. DOI: 10.1103/Phys-RevB.57.R3185.

Iijima, S. (1991). Helical microtubules of graphitic carbon. Na-ture, 354, 56–58. DOI: 10.1038/354056a0.

Jang, J., Oh, J. H., & Stucky, G. D. (2002). Fabricationof ultrafine conducting polymer and graphite nanoparti-cles. Angewandte Chemie International Edition, 41, 4016–4019. DOI: 10.1002/1521-3773(20021104)41:21<4016::AID-ANIE4016>3.0.CO;2-G.

Jang, J. S., & Yoon, H. S. (2003). Fabrication of mag-netic carbon nanotubes using a metal-impregnated poly-mer precursor. Advanced Materials, 15, 2088–2091. DOI:10.1002/adma.200305296.

Jang, J., & Yoon, H. (2005). Multigram-scale fabricationof monodisperse conducting polymer and magnetic carbonnanoparticles. Small, 1, 1195–1199. DOI: 10.1002/smll.200500237.

Janoševic, A., Pašti, I., Gavrilov, N., Mentus, S., Ciric-Marjanovic, G., Krstic, J., & Stejskal, J. (2011). Mi-cro/mesoporous conducting carbonized polyaniline 5-sulfo-salicylate nanorods/nanotubes: Synthesis, characterizationand electrocatalysis. Synthetic Metals, 161, 2179–2184. DOI:10.1016/j.synthmet.2011.08.028.

Janoševic, A., Pašti, I., Gavrilov, N., Mentus, S., Krstic, J.,Mitric, M., Travas-Sejdic, J., & Ciric-Marjanovic, G. (2012).Microporous conducting carbonized polyaniline nanorods:Synthesis, characterization and electrocatalytic properties.Microporous and Mesoporous Materials, 152, 50–57. DOI:10.1016/j.micromeso.2011.12.002.

Jeon, S. S., Han, W. B., An, H. H., Im, S. S., & Yoon, C. S.(2011). Polypyrrole-modified graphitized carbon black as acatalyst support for methanol oxidation. Applied Catalysis

xxx G. Ciric-Marjanovic et al./Chemical Papers

A: General, 409–410, 156–161. DOI: 10.1016/j.apcata.2011.09.044.

Ji, L. W., Yao, Y. F., Toprakci, O., Lin, Z., Liang, Y.Z., Shi, Q., Medford, A. J., Millns, C. R., & Zhang, X.W. (2010). Fabrication of carbon nanofiber-driven elec-trodes from electrospun polyacrylonitrile/polypyrrole bicom-ponents for high-performance rechargeable lithium-ion bat-teries. Journal of Power Sources, 195, 2050–2056. DOI:10.1016/j.jpowsour.2009.10.021.

Jiang, Z. Q., & Jiang, Z. J. (2012). Effects of carbon contenton the electrochemical performance of LiFePO4/C core/shellnanocomposites fabricated using FePO4/polyaniline as aniron source. Journal of Alloys and Compounds, 537, 308–317. DOI: 10.1016/j.jallcom.2012.05.066.

Jin, C., Nagaiah, T. C., Xia, W., Spliethoff, B., Wang, S. S.,Bron, M., Schuhmann, W., & Muhler, M. (2010). Metal-freeand electrocatalytically active nitrogen-doped carbon nano-tubes synthesized by coating with polyaniline. Nanoscale, 2,981–987. DOI: 10.1039/b9nr00405j.

Kim, H., Jung, J. C., Park, D. R., Baeck, S. H., & Song, I.K. (2007). Preparation of H5PMo10V2O40 (PMo10V2) cat-alyst immobilized on nitrogen-containing mesoporous car-bon (N-MC) and its application to the methacrolein oxi-dation. Applied Catalysis A: General, 320, 159–165. DOI:10.1016/j.apcata.2007.01.034.

Kim, H., Jung, J. C., Park, D. R., Lee, H., Lee, J., Lee,S. H., Baeck, S. H., Lee, K. Y., Yi, J., & Song, I. K.(2008). Preparation of H5PMo10V2O40 catalyst immobilizedon nitrogen-containing mesostructured cellular foam carbon(N-MCF-C) and its application to the vapor-phase oxida-tion of benzyl alcohol. Catalysis Today, 132, 58–62. DOI:10.1016/j.cattod.2007.12.004.

Kim, H., Park, D. R., Park, S., Jung, J. C., Lee, S. B., & Song, I.K. (2009). Preparation, characterization, and catalytic activ-ity of H5PMo10V2O40 immobilized on nitrogen-containingmesoporous carbon (PMo10V2/N-MC) for selective conver-sion of methanol to dimethoxymethane. Korean Journal ofChemical Engineering, 26, 660–665. DOI: 10.1007/s11814-009-0110-1.

Kim, K. S., & Park, S. J. (2011). Synthesis of carbon-coated graphene electrodes and their electrochemical perfor-mance. Electrochimica Acta, 56, 6547–6553. DOI: 10.1016/j.electacta.2011.04.092.

Kim, K. S., & Park, S. J. (2012a). Easy synthesis of polyaniline-based mesoporous carbons and their high electrochemicalperformance. Microporous and Mesoporous Materials, 163,140–146. DOI: 10.1016/j.micromeso.2012.04.047.

Kim, K. S., & Park, S. J., (2012b). Synthesis of microporouscarbon nanotubes by templating method and their high elec-trochemical performance. Electrochimica Acta, 78, 147–153.DOI: 10.1016/j.electacta.2012.05.116.

Kroto, H. W, Heath, J. R., O’Brien, S. C., Curl, R. F., & Smal-ley, R. E. (1985). C60: Buckminsterfullerene. Nature, 318,162–163. DOI: 10.1038/318162a0.

Kuo, P. L., & Hsu, C. H. (2011). Stabilization of embeddedPt nanoparticles in the novel nanostructure carbon materi-als. ACS Applied Materials & Interfaces, 3, 115–118. DOI:10.1021/am1010089.

Kuo, P. L., Hsu, C. H., Wu, H. M., Hsu, W. S., & Kuo,D. (2012). Controllable-nitrogen doped carbon layer sur-rounding carbon nanotubes as novel carbon support foroxygen reduction reaction. Fuel Cells, 12, 649–655. DOI:10.1002/fuce.201100130.

Kuroki, S., Nabae, Y., Chokai, M., Kakimoto, M., & Miy-ata, S. (2012). Oxygen reduction activity of pyrolyzedpolypyrroles studied by 15N solid-state NMR and XPS withprincipal component analysis. Carbon, 50, 153–162. DOI:10.1016/j.carbon.2011.08.014.

Kyotani, M., Goto, H., Suda, K., Nagai, T., Matsui, Y., & Ak-agi, K. (2008). Tubular-shaped nanocarbons prepared frompolyaniline synthesized by a self-assembly process and theirelectrical conductivity. Journal of Nanoscience and Nan-otechnology, 8, 1999–2004. DOI: 10.1166/jnn.2008.041.

Langer, J. J., & Golczak, S. (2007). Highly carbonized polyani-line micro- and nanotubes. Polymer Degradation and Stabil-ity, 92, 330–334. DOI: 10.1016/j.polymdegradstab.2006.07.018.

Lei, Z. B., An, L. Z., Dang, L. Q., Zhao, M. Y., Shi, J.Y., Bai, S. Y., & Cao, Y. D. (2009a). Highly dispersedplatinum supported on nitrogen-containing ordered meso-porous carbon for methanol electrochemical oxidation. Mi-croporous and Mesoporous Materials, 119, 30–38. DOI:10.1016/j.micromeso.2008.09.033.

Lei, Z. B., Zhao, M. Y., Dang, L. Q., An, L. Z., Lu, M., Lo, A.Y., Yu, N. Y., & Liu, S. B. (2009b). Structural evolution andelectrocatalytic application of nitrogen-doped carbon shellssynthesized by pyrolysis of near-monodisperse polyanilinenanospheres. Journal of Materials Chemistry, 19, 5985–5995.DOI: 10.1039/b908223a.

Lezanska, M., Pietrzyk, P., & Sojka, Z. (2010). Investiga-tions into the structure of nitrogen-containing CMK-3 andOCM-0.75 carbon replicas and the nature of surface func-tional groups by spectroscopic and sorption techniques. TheJournal of Physical Chemistry C, 114, 1208–1216. DOI:10.1021/jp909529x.

Li, C. C., Yin, X. M., Chen, L. B., Li, Q. H., & Wang, T. H.(2009). Porous carbon nanofibers derived from conductingpolymer: Synthesis and application in lithium-ion batterieswith high-rate capability. The Journal of Physical ChemistryC, 113, 13438–13442. DOI: 10.1021/jp901968v.

Li, X. G., Li, A., Huang, M. R., Liao, Y. Z., & Lu, Y. G. (2010a).Efficient and scalable synthesis of pure polypyrrole nanopar-ticles applicable for advanced nanocomposites and carbonnanoparticles. The Journal of Physical Chemistry C, 114,19244–19255. DOI: 10.1021/jp107435b.

Li, L. M., Liu, E. H., Li, J., Yang, Y. J., Shen, H. J., Huang, Z.Z., & Xiang, X. X. (2010b). Polyaniline-based carbon for asupercapacitor electrode. Acta Physico-Chimica Sinica, 26,1521–1526. DOI: 10.3866/pku.whxb20100626.

Li, L. M., Liu, E. H., Li, J., Yang, Y. J., Shen, H. J., Huang, Z.Z., Xiang, X. X., & Li, W. (2010c). A doped activated car-bon prepared from polyaniline for high performance super-capacitors. Journal of Power Sources, 195, 1516–1521. DOI:10.1016/j.jpowsour.2009.09.016.

Li, L. M., Liu, E. H., Yang, Y. J., Shen, H. J., Huang, Z.Z., & Xiang, X. X. (2010d). Nitrogen-containing carbonsprepared from polyaniline as anode materials for lithiumsecondary batteries. Materials Letters, 64, 2115–2117. DOI:10.1016/j.matlet.2010.06.057.

Li, L. M., Liu, E. H., Shen, H. J., Yang, Y. J., Huang, Z. Z., Xi-ang, X. X., & Tian, Y. Y. (2011). Charge storage performanceof doped carbons prepared from polyaniline for supercapac-itors. Journal of Solid State Electrochemistry, 15, 175–182.DOI: 10.1007/s10008-010-1087-8.

Liao, Y. Z., Li, X. G., & Kaner, R. B. (2010). Facile synthesisof water-dispersible conducting polymer nanospheres. ACSNano, 4, 5193–5202. DOI: 10.1021/nn101378p.

Lin, L., Niu, H. J., Zhang, M. L., Song, W., Wang, Z.,& Bai, X. D. (2008). Electron field emission from amor-phous carbon with N-doped nanostructures pyrolyzed frompolyaniline. Applied Surface Science, 254, 7250–7254. DOI:10.1016/j.apsusc.2008.05.347.

Liu, H. S., Shi, Z., Zhang, J. L., Zhang, L., & Zhang, J. J.(2009). Ultrasonic spray pyrolyzed iron-polypyrrole meso-porous spheres for fuel cell oxygen reduction electrocata-

G. Ciric-Marjanovic et al./Chemical Papers xxxi

lysts. Journal of Materials Chemistry, 19, 468–470. DOI:10.1039/b819619b.

Liu, Z. L., Su, F. B., Zhang, X. H., & Tay, S. W. (2011).Preparation and characterization of PtRu nanoparticles sup-ported on nitrogen-doped porous carbon for electrooxidationof methanol. ACS Applied Materials & Interfaces, 3, 3824–3830. DOI: 10.1021/am2010515.

Liu, Y., Cai, Q., Li, H., & Zhang, J. (2012). Fabricationand characterization of mesoporous carbon nanosheets us-ing halloysite nanotubes and polypyrrole via a template-like method. Journal of Applied Polymer Science. DOI:10.1002/app.38208. (in press)

Long, J. L., Xie, X. Q., Xu, J., Gu, Q., Chen, L. M., & Wang, X.X. (2012). Nitrogen-doped graphene nanosheets as metal-freecatalysts for aerobic selective oxidation of benzylic alcohols.ACS Catalysis, 2, 622–631. DOI: 10.1021/cs3000396.

Lu, Q. F., He, Z. W., Zhang, J. Y., & Lin, Q. L. (2011). Prepa-ration and properties of nitrogen-containing hollow carbonnanospheres by pyrolysis of polyaniline–lignosulfonate com-posites. Journal of Analytical and Applied Pyrolysis, 92, 152–157. DOI: 10.1016/j.jaap.2011.05.009.

Lu, Q. F., He, Z. W., Zhang, J. Y., & Lin, Q. L. (2012). Fab-rication of nitrogen-containing hollow carbon nanospheresby pyrolysis of self-assembled poly(aniline-co-pyrrole). Jour-nal of Analytical and Applied Pyrolysis, 93, 147–152. DOI:10.1016/j.jaap.2011.10.009.

Ma, Y. W., Zhang, L. R., Li, J. J., Ni, H. T., Li, M., Zhang,J. L., Feng, X. M., Fan, Q. L., Hu, Z., & Huang, W. (2011).Carbon-nitrogen/graphene composite as metal-free electro-catalyst for the oxygen reduction reaction. Chinese ScienceBulletin, 56, 3583–3589. DOI: 10.1007/s11434-011-4730-6.

Maiyalagan, T. (2008). Synthesis and electro-catalytic activityof methanol oxidation on nitrogen containing carbon nano-tubes supported Pt electrodes. Applied Catalysis B: Envi-ronmental, 80, 286–295. DOI: 10.1016/j.apcatb.2007.11.033.

Maiyalagan, T., & Viswanathan, B. (2005). Template synthesisand characterization of well-aligned nitrogen containing car-bon nanotubes. Materials Chemistry and Physics, 93, 291–295. DOI: 10.1016/j.matchemphys.2005.03.039.

Mališic, M., Janoševic, A., Šljukic Paunkovic, B., Stojkovic, I.,& Ciric-Marjanovic, G. (2012). Exploration of MnO2/carboncomposites and their application to simultaneous electroan-alytical determination of Pb(II) and Cd(II). ElectrochimicaActa, 74, 158–164. DOI: 10.1016/j.electacta.2012.04.049.

Mentus, S., Ciric-Marjanovic, G., Trchová, M., & Stejskal, J.(2009). Conducting carbonized polyaniline nanotubes. Nan-otechnology, 20, 245601. DOI: 10.1088/0957-4484/20/24/245601.

Mi, H. Y., Xu, Y. L., Shi, W., Yoo, H. D., Park, S. J., Park, Y.W., & Oh, S. M. (2011). Polymer-derived carbon nanofibernetwork supported SnO2 nanocrystals: a superior lithiumsecondary battery material. Journal of Materials Chemistry,21, 19302–19309. DOI: 10.1039/c1jm12262b.

Morávková, Z., Trchová, M., Exnerová, M., & Stejskal, J.(2012a). The carbonization of thin polyaniline films. ThinSolid Films, 520, 6088–6094. DOI: 10.1016/j.tsf.2012.05.067.

Morávková, Z., Trchová, M., Tomšík, E., Čechvala, J., &Stejskal, J. (2012b). Enhanced thermal stability of multi-walled carbon nanotubes after coating with polyaniline salt.Polymer Degradation and Stability, 97, 1405–1414. DOI:10.1016/j.polymdegradstab.2012.05.019.

Murai, T., Fukasawa, R., Muraoka, T., Takauchi, H., Gotoh,Y., Takizawa, T., & Matsuse, T. (2009). Electrical conductiv-ity of microwave heated polyaniline nanotubes and possiblemechanism of microwave absorption by materials. Journal ofMicrowave Power & Electromagnetic Energy, 43(1), 34–43.

Nxumalo, E. N., & Coville, N. J. (2010). Nitrogen doped car-bon nanotubes from organometallic compounds: A review.Materials, 3, 2141–2171. DOI: 10.3390/ma3032141.

Park, S. K., Lee, S. Y., Lee, C. S., Kim, H. M., Joo, J., Beag, Y.W., & Koh, S. K. (2004). High energy (MeV) ion-irradiatedπ-conjugated polyaniline: Transition from insulating state tocarbonized conducting state. Journal of Applied Physics, 96,1914–1918. DOI: 10.1063/1.1769603.

Qie, L., Chen, W. M., Wang, Z. H., Shao, Q. G., Li, X.,Yuan, L. X., Hu, X. L., Zhang, W. X., & Huang, Y. H.(2012). Nitrogen-doped porous carbon nanofiber webs as an-odes for lithium ion batteries with a superhigh capacity andrate capability. Advanced Materials, 24, 2047–2050. DOI:10.1002/adma.201104634.

Qiu, Y. J., Yu, J., Fang, G., Shi, H., Zhou, X. S., & Bai, X.D. (2009). Synthesis of carbon/carbon core/shell nanotubeswith a high specific surface area. The Journal of PhysicalChemistry C, 113, 61–68. DOI: 10.1021/jp806971e.

Rozlívková, Z., Trchová, M., Exnerová, M., & Stejskal, J.(2011). The carbonization of granular polyaniline to producenitrogen-containing carbon. Synthetic Metals, 161, 1122–1129. DOI: 10.1016/j.synthmet.2011.03.034.

Sevilla, M., Mokaya, R., & Fuertes, A. B. (2011a). Ultrahighsurface area polypyrrole-based carbons with superior perfor-mance for hydrogen storage. Energy & Environmental Sci-ence, 4, 2930–2936. DOI: 10.1039/c1ee01608c.

Sevilla, M., Valle-Vigón, P., & Fuertes, A. B. (2011b). N-Doped polypyrrole-based porous carbons for CO2 cap-ture. Advanced Functional Materials, 21, 2781–2787. DOI:10.1002/adfm.201100291.

Shang, S. M., Yang, X. M., & Tao, X. M. (2009). Easysynthesis of carbon nanotubes with polypyrrole nanotubesas the carbon precursor. Polymer, 50, 2815–2818. DOI:10.1016/j.polymer.2009.04.041.

Shiraishi, S., & Mamyouda, H. (2008). Electrochemical capac-itance of carbonized polyaniline. Carbon, 46, 1110. DOI:10.1016/j.carbon.2008.04.003.

Šljukic, B., Stojkovic, I., Cvijeticanin, N., & Ciric-Marjanovic,G. (2011). Hydrogen peroxide sensing at MnO2/carbonizednanostructured polyaniline electrode. Russian Journal ofPhysical Chemistry A, 85, 2406–2409. DOI: 10.1134/s0036024411130279.

Stejskal, J., Trchová, M., & Sapurina, I. (2005). Flame-retardant effect of polyaniline coating deposited on cellulosefibers. Journal of Applied Polymer Science, 98, 2347–2354.DOI: 10.1002/app.22144.

Stejskal, J., Trchová, M., Brodinová, J., & Sapurina, I. (2007).Flame retardancy afforded by polyaniline deposited on wood.Journal of Applied Polymer Science, 103, 24–30. DOI:10.1002/app.23873.

Stejskal, J., Trchová, M., Hromádková, J., Kovářová, J., &Kalendová, A. (2010). The carbonization of colloidal polyani-line nanoparticles to nitrogen-containing carbon analogues.Polymer International, 59, 875–878. DOI: 10.1002/pi.2858.

Stejskal, J., & Trchová, M. (2012). Aniline oligomers ver-sus polyaniline. Polymer International, 61, 240–251. DOI:10.1002/pi.3179.

Stephan, O., Ajayan, P. M., Colliex, C., Redlich, Ph., Lambert,J. M., Bernier, P., & Lefin, P. (1994). Doping graphitic andcarbon nanotube structures with boron and nitrogen. Sci-ence, 266, 1683–1685. DOI: 10.1126/science.266.5191.1683.

Su, F. B., Tian, Z. Q., Poh, C. K., Wang, Z., Lim, S. H., Liu,Z. L., & Lin, J. Y. (2010). Pt nanoparticles supported onnitrogen-doped porous carbon nanospheres as an electrocat-alyst for fuel cells. Chemistry of Materials, 22, 832–839. DOI:10.1021/cm901542w.

Su, F. B., Poh, C. K., Chen, J. S., Xu, G. W., Wang, D., Li, Q.,Lin J. Y., & Lou, X. W. (2011). Nitrogen-containing micro-

xxxii G. Ciric-Marjanovic et al./Chemical Papers

porous carbon nanospheres with improved capacitive prop-erties. Energy & Environmental Science, 4, 717–724. DOI:10.1039/c0ee00277a.

Tan, Y. M., Xu, C. F., Chen, G. G., Fang, X. L., Zheng, N. F.,& Xie, Q. J. (2012). Facile synthesis of manganese-oxide-containing mesoporous nitrogen-doped carbon for efficientoxygen reduction. Advanced Functional Materials, 22, 4584–4591. DOI: 10.1002/adfm.201201244.

Trchová, M., Matějka, P., Brodinová, J., Kalendová, A.,Prokeš, J., & Stejskal, J. (2006). Structural and conduc-tivity changes during the pyrolysis of polyaniline base.Polymer Degradation and Stability, 91, 114–121. DOI:10.1016/j.polymdegradstab.2005.04.022.

Trchová, M., Konyushenko, E. N., Stejskal, J., Kovářová, J.,& Ciric-Marjanovic, G. (2009). The conversion of polyani-line nanotubes to nitrogen-containing carbon nanotubesand their comparison with multi-walled carbon nanotubes.Polymer Degradation and Stability, 94, 929–938. DOI:10.1016/j.polymdegradstab.2009.03.001.

Trchová, M., Morávková, Z., Šeděnková, I., & Stejskal, J. (2012).Spectroscopy of thin polyaniline films deposited during chem-ical oxidation of aniline. Chemical Papers, 66, 415–445. DOI:10.2478/s11696-012-0142-6.

Villalpando-Paez, F., Zamudio, A., Elias, A. L., Son, H., Bar-ros, E. B., Chou, S. G., Kim, Y. A., Muramatsu, H., Hayashi,T., Kong, J., Terrones, H., Dresselhaus, G., Endo, M., Ter-rones, M., & Dresselhaus, M. S. (2006). Synthesis and char-acterization of long strands of nitrogen-doped single-walledcarbon nanotubes. Chemical Physics Letters, 424, 345–352.DOI: 10.1016/j.cplett.2006.04.074.

Wang, Y., Su, F. B., Wood, C. D., Lee, J. Y., & Zhao,X. S. (2008a). Preparation and characterization of carbonnanospheres as anode materials in lithium-ion secondary bat-teries. Industrial & Engineering Chemistry Research, 47,2294–2300. DOI: 10.1021/ie071337d.

Wang, Y. G., Wang, Y. R., Hosono, E. J., Wang, K. X.,& Zhou, H. S. (2008b). The design of a LiFePO4/carbonnanocomposite with a core–shell structure and its synthe-sis by an in situ polymerization restriction method. Ange-wandte Chemie International Edition, 47, 7461 –7465. DOI:10.1002/anie.200802539.

Wang, T., He, J. P., Sun, D., Guo, Y. X., Ma, Y. O., Hu, Y.,Li, G. X., Xue, H. R., Tang, J., & Sun, X. (2011a). Syn-thesis of mesoporous carbon-silica-polyaniline and nitrogen-containing carbon-silica films and their corrosion behav-ior in simulated proton exchange membrane fuel cells en-vironment. Journal of Power Sources, 196, 9552–9560. DOI:10.1016/j.jpowsour.2011.07.084.

Wang, R. F., Jia, J. C., Li, H., Li, X. S., Wang, H., Chang, Y.M., Kang, J., & Lei, Z. Q. (2011b). Nitrogen-doped carboncoated palygorskite as an efficient electrocatalyst support foroxygen reduction reaction. Electrochimica Acta, 56, 4526–4531. DOI: 10.1016/j.electacta.2011.02.066.

Wu, G., Chen, Z. W., Artyushkova, K., Garzon, F. H., & Zele-nay, P. (2008a). Polyaniline-derived non-precious catalyst forthe polymer electrolyte fuel cell cathode. In T. Fuller, K. Shi-nohara, V. Ramani, P. Shirvanian, H. Uchida, S. Cleghorn,M. Inaba, S. Mitsushima, P. Strasser, H. Nakagawa, H. A.Gasteiger, T. Zawodzinski, & C. Lamy (Eds.), ECS Trans-actions (Vol. 16, pp. 159–170). Pennington, NJ, USA: Elec-trochemical Society. DOI: 10.1149/1.2981852.

Wu, G., Li, D. Y., Dai, C. S., Wang, D. L., & Li, N. (2008b).Well-dispersed high-loading Pt nanoparticles supported byshell–core nanostructured carbon for methanol electrooxida-tion. Langmuir, 24, 3566–3575. DOI: 10.1021/la7029278.

Wu, G., Swaidan, R., Li, D. Y., & Li, N. (2008c). Enhancedmethanol electro-oxidation activity of PtRu catalysts sup-

ported on heteroatom-doped carbon. Electrochimica Acta,53, 7622–7629. DOI: 10.1016/j.electacta.2008.03.082.

Wu, G., Artyushkova, K., Ferrandon, M., Kropf, A. J., My-ers, D., & Zelenay, P. (2009). Performance durability ofpolyaniline-derived non-precious cathode catalysts. ECSTransactions, 25, 1299–1311. DOI: 10.1149/1.3210685.

Wu, G., More K. L., Johnston, C. M., & Zelenay, P. (2011).High-performance electrocatalysts for oxygen reduction de-rived from polyaniline, iron, and cobalt. Science, 332, 443–447. DOI: 10.1126/science.1200832.

Xiang, X. X., Liu, E. H., Huang, Z. Z., Shen, H. J., Tian, Y. Y.,Xiao, C. Y., Yang, J. J., & Mao, Z. H. (2011a). Preparation ofactivated carbon from polyaniline by zinc chloride activationas supercapacitor electrodes. Journal of Solid State Electro-chemistry, 15, 2667–2674. DOI: 10.1007/s10008-010-1258-7.

Xiang, X. X., Liu, E. H., Huang, Z. Z., Shen, H. J., Tian, Y. Y.,Xiao, C. Y., Yang, J. J., & Mao, Z. H. (2011b). Microporouscarbon derived from polyaniline base as anode material forlithium ion secondary battery. Materials Research Bulletin,46, 1266–1271. DOI: 10.1016/j.materresbull.2011.03.032.

Xiang, X. X., Huang, Z. Z., Liu, E. H., Shen, H. J., Tian, Y.Y., Xie, H., Wu, Y. H., & Wu, Z. L. (2011c). Lithium storageperformance of carbon nanotubes prepared from polyanilinefor lithium-ion batteries. Electrochimica Acta, 56, 9350–9356.DOI: 10.1016/j.electacta.2011.08.014.

Xiang, X. X., Liu, E. H., Li, L. M., Yang Y. J., Shen, H. J.,Huang, Z. Z., & Tian, Y. Y. (2011d). Activated carbon pre-pared from polyaniline base by K2CO3 activation for applica-tion in supercapacitor electrodes. Journal of Solid State Elec-trochemistry, 15, 579–585. DOI: 10.1007/s10008-010-1130-9.

Yan, H., Inokuchi, M., Kinoshita, M., & Toshima, N. (2005).Spontaneously formed polypyrrole microtubes: incandes-cence and graphitization. Synthetic Metals, 148, 93–98. DOI:10.1016/j.synthmet.2004.08.036.

Yan, J., Wei, T., Qiao, W. M., Fan, Z. J., Zhang, L. J., Li, T.Y., & Zhao, Q. K. (2010). A high-performance carbon derivedfrom polyaniline for supercapacitors. Electrochemistry Com-munications, 12, 1279–1282. DOI: 10.1016/j.elecom.2010.06.037.

Yang, C. M., Weidenthaler, C., Spliethoff, B., Mayanna, M., &Schuth, F. (2005). Facile template synthesis of ordered meso-porous carbon with polypyrrole as carbon precursor. Chem-istry of Materials, 17, 355–358. DOI: 10.1021/cm049164v.

Yang, M. M., Cheng, B., Song, H. H., & Chen, X. H.(2010). Preparation and electrochemical performance ofpolyaniline-based carbon nanotubes as electrode material forsupercapacitor. Electrochimica Acta, 55, 7021–7027. DOI:10.1016/j.electacta.2010.06.077.

Yao, T. J., Cui, T. Y., Wu, J., Chen, Q. Z., Yin, X. J., Cui, F.,& Sun, K. N. (2012). Preparation of acid-resistant core/shellFe3O4@C materials and their use as catalyst supports. Car-bon, 50, 2287–2295. DOI: 10.1016/j.carbon.2012.01.048.

Yin, X. G., Huang, K. L., Liu, S. Q., Wang, H. Y., & Wang,H. (2010a). Preparation and characterization of Na-dopedLiFePO4/C composites as cathode materials for lithium-ionbatteries. Journal of Power Sources, 195, 4308–4312. DOI:10.1016/j.jpowsour.2010.01.019.

Yin, J. B., Xia, X. A., Xiang, L. Q., & Zhao, X. P. (2010b).Conductivity and polarization of carbonaceous nanotubes de-rived from polyaniline nanotubes and their electrorheologywhen dispersed in silicone oil. Carbon, 48, 2958–2967. DOI:10.1016/j.carbon.2010.04.035.

Yin, J. B., Xia, X. A., Xiang, L. Q., & Zhao, X. P. (2011).Temperature effect of electrorheological fluids based onpolyaniline derived carbonaceous nanotubes. Smart Materi-als & Structures, 20, 015002. DOI: 10.1088/0964-1726/20/1/015002.

G. Ciric-Marjanovic et al./Chemical Papers xxxiii

Yin, J. B., Shui, Y. J., Chang, R. T., & Zhao, X. P.(2012). Graphene-supported carbonaceous dielectric sheetsand their electrorheology. Carbon, 50, 5247–5255. DOI:10.1016/j.carbon.2012.06.062.

Yuan, D. S., Zhou, T. X., Zhou, S. L., Zou, W. J., Mo, S. S.,& Xia, N. N. (2011). Nitrogen-enriched carbon nanowiresfrom the direct carbonization of polyaniline nanowires andits electrochemical properties. Electrochemistry Communi-cations, 13, 242–246. DOI: 10.1016/j.elecom.2010.12.023.

Zhang, X. Y., & Manohar, S. K. (2006). Microwave synthesis ofnanocarbons from conducting polymers. Chemical Commu-nications, 2006, 2477–2479. DOI: 10.1039/b603925a.

Zhou, Y. K., Neyerlin, K., Olson, T. S., Pylypenko, S., Bult,J., Dinh, H. N., Gennett, T., Shao, Z. P., & O’Hayre, R.(2010). Enhancement of Pt and Pt-alloy fuel cell catalystactivity and durability via nitrogen-modified carbon sup-ports. Energy & Environmental Science, 3, 1437–1446. DOI:10.1039/c003710a.

Zhou, C. F., Liu, Z. W., Du, X. S., Mitchell, D. R. G.,Mai, Y. W., Yan, Y. S., & Ringer, S. (2012). Hollownitrogen-containing core/shell fibrous carbon nanomaterialsas support to platinum nanocatalysts and their TEM to-mography study. Nanoscale Research Letters, 7, 165. DOI:10.1186/1556-276x-7-165.

Zhu, Y., Li, J. M., Wan, M. X., & Jiang, L. (2009). Electromag-netic functional urchin-like hollow carbon spheres carbonizedby polyaniline micro/nanostructures containing FeCl3 as aprecursor. European Journal of Inorganic Chemistry, 2009,2860–2864. DOI: 10.1002/ejic.200900040.