Self-powered electrochemical anodic oxidation: A new

Nano Res

1

Self-powered electrochemical anodic oxidation: A new

method for preparation of mesoporous Al2O3 without

applying electricity

Huarui Zhu1, Ying Xu1, Yu Han1, Shuwen Chen1, Tao Zhou1, Magnus Willander1, Xia Cao1,2 (), and

Zhonglin Wang1,3 ()

Nano Res., Just Accepted Manuscript • DOI 10.1007/s12274-015-0860-5

http://www.thenanoresearch.com on July 13, 2015

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Nano Research

DOI 10.1007/s12274-015-0860-5

Self-powered electrochemical anodic oxidation: a new



Huarui Zhu, 1 Ying Xu, 1 Yu Han, 1 Shuwen Chen, 1 Tao

Zhou, 1 Magnus Willander, 1 Xia Cao*, 1, 2 and Zhonglin

Wang*, 1, 3

1 Beijing Institute of Nanoenergy and Nanosystems,

Chinese Academy of Sciences, Beijing 100083, China

2 School of Chemistry and Biological Engineering,

University of Science & Technology Beijing, Beijing,

100083, China

3 School of Material Science and Engineering, Georgia

Institute of Technology, Atlanta, Georgia 30332-0245,

USA

The first self-powered electrochemical anodic oxidization system was

developed which is capable of synthesis of mesoporous Al2O3 driven

by TENG arrays without applying electricity.

Corresponding Authors:

*E-mail: [email protected].

*E-mail: [email protected].




Huarui Zhu, 1 Ying Xu, 1 Yu Han, 1 Shuwen Chen, 1 Tao Zhou, 1 Magnus Willander, 1 Xia Cao, 1, 2 () and

Zhonglin Wang, 1, 3 ()

Received: day month year

Revised: day month year

Accepted: day month year

(automatically inserted by

the publisher)

© Tsinghua University Press

and Springer-Verlag Berlin

Heidelberg 2014

KEYWORDS

triboelectric

nanogenerator,

self-powered

electrochemical anodic

oxidization, mesoporous

materials

ABSTRACT

Anodic oxidization (AO) is one of the most important methods to fabricate

mesoporous Al2O3, which can be conducted at either high potential or low

potential, but an external electricity power source is indispensible. In this work,

a novel self-powered electrochemical anodic oxidization (SPAO) system is

introduced for preparing mesoporous Al2O3 by using the newly invented

triboelectric nanogenerator (TENG) arrays driven by natural wind. Owing to

the controllable voltage output of TENG arrays, the SPAO system can regulate

the pore’s depth and size of mesoporous Al2O3. Distinguished from traditional

AO system, our technique takes the advantages of high output voltage of TENG

arrays without additional energy cost. In addition, the SPAO system can be

used for the preparation of other mesoporous materials.

1 Introduction

Mesoporous aluminum oxides (Al2O3) often display

novel physical, chemical, and mechanical properties

due to their high surface-to-volume ratio and low

densities, such as increased chemical activity and

high specific strength, which could be used as

catalyst beds, molecular sieves and hosts for

inclusion compounds [1-4]. In the synthesis of

mesoporous Al2O3, anodic oxidization is one of the

most important methods because it is relatively

simple and can be conducted at either high potential

or low potential, although the detailed mechanisms

are still under discussion [5, 6]. However, the

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Address correspondence to [email protected]; [email protected].

Research Article

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2 Nano Res.

application of anodic oxidation for preparation of

mesoporous Al2O3 has one major disadvantages, that

is an applied potential is required as the driving force

of the oxidation system [7-11].

Currently, triboelectric nanogenerator, as an

innovative invention, have been developed to convert

mechanical energy from irregular mechanical

vibrations to electricity, such as impacts [12, 13],

sliding [14, 15], and rotations [16, 17]. TENG exhibits

the remarkable characteristics of easy fabrication,

low cost, and high efficiency. Moreover, the output

potential of TENG is adjustable, that is the output

potential can vary from several volt to a few hundred

volt based on the contact electrification effect of

TENG [18]. Previously, we have proposed the

self-powered electrochemistry for applications of

such as water splitting, environmental particular

filtering, water purification and pollution cleaning

[19-21].

In this paper, instead of utilizing an external

electricity power, we designed a self-powered

electrochemical AO system for the preparations of

mesoporous Al2O3 by using 3×3 TENG arrays driven

by the energy harvested from natural wind. It is

worth noting that the TENG arrays can harvest wind

energy from all directions and the electrical output of

the TENG arrays can be adjusted according to the

frequency. In addition, the pore size and depth of the

prepared mesoporous Al2O3 could be regulated from

the vibrational frequency of TENG arrays & the

reaction times. Last but not the least; the SPAO

system is temperate, easy to be applied and

controlled, making it feasible for preparation of other

mesoporous materials.

2 Results and discussion

2.1 Fabrication and characterization of TENG arrays

In order to evaluate the feasibility of the SPAO

system, electrical characteristics of the TENG arrays

were investigated first. The TENG is based on the

contact electrification of polydimethylsiloxane

(PDMS) and ITO, where PDMS was pretreated to

form inverted pyramid structures (Figure 1d). In

order to improve the efficiency of TENG arrays, 3×3

TENG cells were used in the SPAO system (Figures

Figure 1 (a) Scheme of the designed TENG, (b) profile of single

TENG cell, (c) profile of TENG arrays consisted of 3×3 TENG

cells; (d) SEM image of PDMS’ pyramid structures; (e) Short

circuit currents and (f) open circuit voltages of single TENG cell

at a frequency of 3 Hz; (g) Schematic diagram of the AO system

driven by TENG arrays; (h) Lighted LEDs as driven by wind

blowing.

1a-c). Figure 1e and 1f show the output current and

voltage of a single TENG cell under stimulations at a

certain frequency of 3 Hz stressed by a linear

mechanical motor. As we can see, the output current

is over 0.65 mA, and the voltage reaches about 256 V.

For the AO system powered with TENG, the cathode

was Ti plate that was immersed into the electrolyte

and the anode was Al foil. The TENG arrays was

rectified and then connected to the whole system

with the external stimulation at different frequencies

(Figure 1g). Furthermore, TENG arrays can harvest

the mechanical energy of winds, and then convert

them into electricity to provide the power for the AO

system [13, 22]. As shown in Figure 1h, multiple

light-emitting diodes (LEDs, which are arranged in

letters S P A O) were powered up driven by wind

(Detail process see video S, in supporting

information), which indicated that the SPAO system

is feasible.

2.2 Morphology characterization of mesoporous

Al2O3 synthesized by SPAO system

To get intact mesoporous Al2O3, two-step anodization

under potentiostatic mode driven by TENG arrays

was employed in this work and the synthetic process

was displayed in Figure 2. During the experiment, 1.0

www.theNanoResearch.com∣www.Springer.com/journal/12274 | Nano Research

3 Nano Res.

Figure 2 Schematic diagrams for the synthetic process of

mesoporous Al2O3.

mol/L sulfuric acid solutions were employed under

potentiostatic modes which were controlled by the

vibrational frequency of TENG arrays. It is worth

noting that aluminum oxide must be removed

thoroughly before the second anodization step. At

the end of the experiment, the remaining aluminum

substrate was removed in a mixed solution of

HCl/CuCl2 [23].

At the same time, the morphologies and sizes of

typical mesoporous Al2O3 with different frequencies

of TENG arrays & reaction times were characterized

by SEM, as shown in Figure 3. Figure 3a shows the

intact pore structures obtained using different

anodization potential from changing the stimulating

frequencies of TENG arrays. From the scale size of

Figure 3a, we can see that the pore size of the of the

mesoporous Al2O3 increase from 10 nm to 50 nm with

the anodization potential increasing. However, at

higher anodization potentials, the mesoporous

structures are visibly damaged in many regions

(Figure S1a in the ESM). At the same time, the

influence of reaction times on the pore size of

samples was also studied. Figure 3b shows the

changes of the pore’s depth and size of samples with

the reaction times. It is apparent that the pore’s depth

and size of mesoporous Al2O3 are both increased

with the reaction time elapsing. These images also

describe the formation of these mesoporous samples.

What’s more, the channels of these specimens grow

straight. However, if aluminum oxide can’t remove

thoroughly before the second anodization step, the

prepared mesoporous samples contain many

irregular small pores around the original pore. These

excess pores are not vertical and seen as branch pore

structures which have been reported in the literatures

(Figure S1b in the ESM) [24].

Figure 3 SEM images of the synthesized mesoporous Al2O3,

(a) the same reaction time (2 h) with different vibrational

frequencies (fa1 to fa4 is 1, 3, 5, 7 Hz, respectively) of TENG

arrays, (b) the same vibrational frequency (3 Hz) of TENG

arrays with different reaction times (tb1 to tb4 is 0, 1, 1.5, 2 h,

respectively); and (c) EDX spectra of the mesoporous Al2O3

structures.

In the meantime, these mesoporous specimens

were also identified by energy-dispersive X-ray (EDX)

analysis. As shown in Figure 3c, the signals of O and

Al elements are observed in the EDX spectra, which

confirm that the mesoporous material is Al2O3. The

SEM images and EDX spectra demonstrate that the

intact mesoporous Al2O3 are prepared from the SPAO

system and the pore’s depth and size of the

mesoporous material could be controlled from the

frequency of TENG arrays & reaction times.

Moreover, the pore’s depth and size of mesoporous

material are both increased with the increase of

vibrational frequency & reaction time.

2.3 Principle for self-powered formation of

mesoporous Al2O3

In the self-powered electrochemical anodic

oxidization process, the formation of mesoporous

Al2O3 can be expressed in formulas (1) and (2),

respectively [25, 26].

Anode: Al → Al3+ + 3e（priority）(1-1)

4OH- → 2H2O + O2 + 4e（secondary）(1-2)


4 Nano Res.

4Al3+ + 3O2 → 2Al2O3

Al2O3 + 6H+→ 2Al3+ + 3H2O

Cathode: 2H+ + 2e → H2（priority）(2)

To improve the efficiency of the SPAO system, the

continuous AC output from the TENG arrays was

tuned by using the conventional transformer [19]. As

shown in Figure 4a, the open circuit potential was

reduced to about 17 V at the certain frequency of 3

Hz. At the same time, the relationship between the

transformed potential of AO system and the

triggering frequency of TENG arrays was also

studied. The corresponding transformed potential

changes of the AO system at different frequency is

shown in Figure 4b, and it is obvious that the

transformed potential of the system increased from

12.14 V to 28.82 V when the vibrational frequency

increased from 1 Hz to 9 Hz. What’s more, the value

of the transformed potential charges is almost

proportional to the frequency (as shown in Figure

4c).

Figure 4 (a) Open-circuit voltage of a single TENG cell

after applying a transformer at the frequency of 3 Hz, (b) the

transformed voltage changes of single TENG cell at

different vibrational frequencies stressed by linear

mechanical motor, (c) the relationship between the

transformed voltage with different vibrational frequencies

from 1 Hz to 9 Hz; (d) Nitrogen adsorption-desorption

isotherm of the mesoporous Al2O3 (t: 2h, f: 3Hz) and its

pore size distribution (inset) calculated from the BJH model.

In the self-powered electrochemical anodic

oxidization system, when electrolyte concentration

and temperature were set to certain values at

constant potential, a critical current density (Jc) must

be present [27, 28] and the mesoporous structure

could only be formed when the current density is

below the critical density. In this initial event,

aluminum is oxidized quickly. At the same time, OH-

migrates from cathode to anode. Lots of Al3+

concentrated on the anode at the beginning, which

lead to a compact Al2O3 layer on the aluminum

surface. The formation of the compact Al2O3 layer

will increase the voltage and electric field. Then the

dissolution rate of the compact Al2O3 layer will

accelerate to lower the voltage and electric field.

Finally, the growth of mesoporous Al2O3 occurs when

Al2O3 is formed at the same rate as that it is dissolved.

Meanwhile, the increase of temperature or electrolyte

concentration can speed up the rate of vertical and

horizontal dissolution of aluminum oxide. During

the anodizing process, higher anodization potential

results in the corresponding higher current density,

which lead to the increase of pore size and depth of

mesoporous material [29, 30]. Therefore, the pore size

and depth of the mesoporous Al2O3 increase with the

TENG arrays’ vibrational frequency increasing,

which is consistent with the SEM results.

2.4 N2 adsorption-desorption study on mesoporous

Al2O3

Figure 4d shows the N2 adsorption-desorption

isotherm and the corresponding pore size

distribution of mesoporous Al2O3 (t: 2h, f: 3Hz). They

could be classified as type Ⅰ isotherm characteristic

of mesoporous materials, indicating that the sample

have a mesoporous structure [31, 32]. In the relative

pressure range of P/P0= 0.10-0.88, the adsorbed

amount gradually increases for the sample, but above

P/P0> 0.88, N2 uptake becomes saturated. From the

pore distribution curve measured by the

Barrett-Joyner-Halenda (BJH) method (inset), one can

see that the sample have an average pore diameter of

about 42 nm. For the mesoporous Al2O3, the BET

surface area and the total pore volume are 216.3 m2

g-1 and 0.2597 cm3 g-1 respectively. These results

reveal that pore sizes obtained from N2 sorption

analysis agree well with those obtained from SEM

image analysis independently.


5 Nano Res.

3 Conclusions

In summary, we developed the first self-powered

electrochemical anodic oxidization system that is

capable of synthesis of mesoporous Al2O3 driven by

TENG arrays using the energy provided by natural

wind in the environment. Systematic studies have

found that the pore depth and size of mesoporous

Al2O3 can be regulated by changing the stimulating

frequency of the TENG arrays. What’s more, BET

data further confirm that the prepared materials have

mesoporous structures. The temperate, easy

controlled self-powered electrochemical AO system

is very feasible for preparation of other mesoporous

materials.

4 Experimental section

4.1 Fabrication of the self-powered AO system

The basic structure of the SPAO system is composed

of TENG arrays device and an electrochemical AO

system, as schematically illustrated in Figure 1. The

TENG arrays consist of 3×3 TENG cells. Each one is

based on the contact electrification of PDMS and ITO

(Figure 1a). The fabrication of TENG has been

described in detail previously [21, 33]. In a typical

procedure, PDMS film was transferred onto an

ITO-coated polyester (PET) film. Then, another clean

ITO-coated PET film was placed onto the prepared

PDMS-ITO-PET film and sealed at the two ends,

leaving a small gap of 3 mm between the two contact

surfaces by forming an arched structure. The

effective size of TENG cell is 9 cm×9 cm, and the total

thickness is about 1 mm. The output voltage and

current were measured by the Keithley 6514 System

Electrometer and SR570 low noise current amplifier

from Stanford Research Systems. In the self-powered

electrochemical AO system, the anode was aluminum

foils that were immersed into the electrolyte and the

cathode was Ti plates.

4.2 Preparation of mesoporous Al2O3

High purity aluminum foils (99.99%,

15mm×10mm×0.2mm) were used as working

electrodes. In order to get the uniform mesoporous

materials, two-step anodization was employed for

the process [34, 35]. Prior to anodization, the

aluminum foils were degreased by ultrasonic in

ethanol for 10 min and then electro-polished in a

mixture solution of HClO4 and ethanol

(VHClO4/Vethanol=1/4) at 20 V for 5min. Then 1.0 mol/L

sulfuric acid solutions were employed under

potentiostatic modes which were controlled by the

frequency of TENG arrays. Following the first

anodization step, the specimens were immersed in 6

wt % phosphoric acid for 0.5 h to remove aluminum

oxide then proceeded second anodization in

conditions as same as the first step. In the whole

process of oxidation, a powerful ice-water bath

system was used to maintain the low temperature

needed for the high-field anodization. Subsequently,

the as-anodized sample was immersed into a mixture

solution of 0.2 mol/L CuCl2 and 6.1 mol/L HCl to

remove the underlying Al substrate [23, 36].

4.3 Characterization

Scanning electron microscopy (SEM) images

equipped with an EDX spectrometer were collected

to analyze the surface morphology and

microstructure of mesoporous Al2O3. The 1 kV

accelerating voltage was used to avoid damaging the

mesoporous microstructure. The porosity and

specific surface areas of the yielded mesoporous

Al2O3 was substantiated by adsorption-desorption of

ultrapure N2 on a Micromeritics ASAP 2020 unit at

313 K.

Acknowledgements

We thank the financial support from the National

Natural Science Foundation of China (NSFC No.

21173017, 51272011 and 21275102), the Program for

New Century Excellent Talents in University

(NCET-12-0610), the science and technology research

projects from education ministry (213002A), National

“Twelfth Five-Year” Plan for Science & Technology

Support (No.2013BAK12B06), the “thousands

talents” program for pioneer researcher and his

innovation team, China, National Natural Science

Foundation of China (Grant No. 51432005;

No.Y4YR011001), Beijing City Committee of science

and technology (Z131100006013004,

Z131100006013005).


6 Nano Res.

Electronic Supplementary Material: Supplementary

material (SEM images of mesoporous Al2O3 without

growing straight, included Figure S1a, S1b; Video of

multiple light-emitting diodes (LEDs) powered up

driven by wind.) is available in the online version of

this article at

http://dx.doi.org/10.1007/s12274-***-****-*

References

[1] Lu, Q.; Gao, F.; Komarneni, S.; Mallouk, T. E. Ordered

SBA-15 Nanorod Arrays Inside a Porous Alumina

Membrane. J. Am. Chem. Soc. 2004, 126, 8650-8651.

[2] Bagshaw, S. A.; Pinnavaia, T. J. Mesoporous alumina

molecular sieves. Angew. Chem. Int. Ed. 1996, 35,

1102-1105.

[3] Cabrera, S.; Haskouri, J. E.; Alamo, J.; Beltran, A.; Beltran,

D.; Mendioroz, S.; Marcos, D. M.; Amoros, P.

Surfactant-Assisted Synthesis of Mesoporous Alumina

Showing Continuously Adjustable Pore Sizes. Adv. Mater.

1999, 11, 379-381.

[4] Zhang, W.; Pinnavaia, T. J. Rare earth stabilization of

mesoporous alumina molecular sieves assembled through

an N○ I○ pathway. Chem. Commun. 1998, 1185-1186.

[5] Masuda, H.; Fukuda, F. Ordered metal nanohole arrays

made by a two-step replication of honeycomb structures of

anodic alumina. Science 1995, 268, 1466-1468.

[6] Masuda, H.; Yamada, H.; Satoh, M.; Asoh, H.; Nakao, M.

Highly ordered nanochannel-array architecture in anodic

alumina. Appl. Phys. Lett. 1997, 71, 2770-2772.

[7] Montero-Moreno, J. M.; Belenguer, M.; Sarret, M.; Müller,

C. M. Production of alumina templates suitable for

electrodeposition of nanostructures using stepped

techniques. Electrochimica Acta 2009, 54, 2529-2535.

[8] Yanagishita, T.; Sasaki, M.; Nishio, K.; Masuda, H. Carbon

Nanotubes with a Triangular Cross-section, Fabricated

Using Anodic Porous Alumina as the Template. Adv. Mater.

2004, 16, 429-432.

[9] Nielsch, K.; Choi, J.; Schwim, K.; Wehrspohn, R. B.;

Gösele, U. Self-ordering regimes of porous alumina: the 10

porosity rule. Nano Lett. 2002, 2, 677-680.

[10] Jessensky, O.; Müller, F.; Gösele, U. Self-organized

formation of hexagonal pore arrays in anodic alumina. Appl.

Phys. Lett. 1998, 72, 1173-1175.

[11] Lee, W.; Ji, R.; Goesele, U.; Nielsch, K. Fast fabrication

of long-range ordered porous alumina membranes by hard

anodization. Nat Mater. 2006, 5, 741-747.

[12] Zhu, G.; Su, Y. J.; Bai, P.; Chen, J.; Jing, Q. S.; Yang,

W. Q.; Wang, Z. L. Harvesting Water Wave Energy by

Asymmetric Screening of Electrostatic Charges on a

Nanostructured Hydrophobic Thin-Film Surface. ACS Nano

2014, 8, 6031-6037.

[13] Wen, X. N.; Yang, W. Q.; Jing, Q. S.; Wang, Z. L.

Harvesting Broadband Kinetic Impact Energy from

Mechanical Triggering/Vibration and Water Waves. ACS

Nano 2014, 8, 7405-7412.

[14] Jing, Q. S.; Zhu, G.; Bai, P.; Xie, Y. N.; Chen, J. R.;

Han, P. S.; Wang, Z. L. Case-encapsulated triboelectric

nanogenerator for harvesting energy from reciprocating

sliding motion. ACS Nano 2014, 8, 3836-3842.

[15] Lin, L.; Wang, S. H.; Xie, Y. N.; Jing, Q. S.; Niu, S. M.;

Hu, Y. F.; Wang, Z. L. Segmentally structured disk

triboelectric nanogenerator for harvesting rotational

mechanical energy. Nano Lett. 2013, 13, 2916-2919.

[16] Jing, Q. S.; Zhu, G.; Bai, P.; Xie, Y. N.; Chen, J. R.; Han,

P. S.; Wang, Z. L. Triboelectric nanogenerator built on

suspended 3D spiral structure as vibration and positioning

sensor and wave energy harvester. ACS Nano 2013, 7,

10424-10432.

[17] Zhu, G.; Chen, J.; Zhang, T. J.; Jing, Q. S.; Wang, Z. L.

Radial-arrayed rotary electrification for high performance

triboelectric generator. Nat. Commun. 2014, 5, 3426-3434.

[18] Guo, W. X.; Li, X. Y.; Chen, M. X.; Xu, L.; Dong, L.;

Cao, X.; Tang, W.; Zhu, J.; Lin, Ch-J.; Pan, C. F.; Wang, Z.

L. Electrochemical Cathodic Protection Powered by

Triboelectric Nanogenerator. Adv. Funct. Mater. 2014, 24,

6691-6700.

[19] Tang, W.; Han, Y.; Han, C. B.; Gao, C. Z.; Cao, X.;

Wang, Z. L. Self-Powered Water Splitting Using Flowing

Kinetic Energy. Adv. Mater. 2015, 27, 272-276.

[20] Chen, S. W.; Gao, C. Z.; Tang, W.; Zhu, H. R.; Cao, X.;

Wang, Z. L. Self-powered cleaning of air pollution by wind

http://dx.doi.org/10.1007/s12274-***-****-*


7 Nano Res.

driven triboelectric nanogenerator. Nano Energy 2015,

doi:10.1016/j.nanoen.2014.12.013.

[21] Zhu, H. R.; Tang, W.; Gao, C. Z.; Han, Y.; Li, T.; Cao,

X.; Wang, Z. L. Self-powered Metal Surface Anti-corrosion

Protection Using Energy Harvested from Rain Drops and

Wind. Nano Energy 2015, DOI:

10.1016/j.nanoen.201411041.

[22] Yang, W. Q.; Chen, J.; Zhu, G.; Yang, J.; Bai, P.; Su, Y.

J.; Jing, Q. S.; Wang, Z. L. Harvesting energy from the

natural vibration of human walking. ACS Nano 2013, 7,

11317-11324.

[23] Zhao, S.; Chan, K.; Yelon, A.; Veres, T. Novel structure

of AAO film fabricated by constant current anodization.

Adv. Mater. 2007, 19, 3004-3007.

[24] Li, D.; Zhao, L.; Jiang, C.; Lu, J. G. Formation of anodic

aluminum oxide with serrated nanochannels. Nano Lett.

2010, 10, 2766-2771.

[25] Chung, C. K.; Zhou, R. X.; Liu, T. Y.; Chang, W. T.

Hybrid pulse anodization for the fabrication of porous

anodic alumina films from commercial purity (99%)

aluminum at room temperature. Nanotechnology 2009, 20,

055301.

[26] Chung, C. K.; Chang, W. T.; Liao, M. W.; Chang, H. C.

Effect of pulse voltage and aluminum purity on the

characteristics of anodic aluminum oxide using hybrid pulse

anodization at room temperature. Thin Solid Films 2011,

519, 4754-4758.

[27] Xu, Y.; Thompson, G. E.; Wood, G. C. Mechanism of

anodic film growth on aluminium. Trans. Inst. Met. Finish.

1985, 63, 98-103.

[28] O’Sullivan, J. P.; Wood, G. C. The morphology and

mechanism of formation of porous anodic films on

aluminium. Proc. R Soc. Lond A. 1970, 317, 511-543.

[29] Ono, S.; Saito, M.; Asoh, H. Fabrication of porous

anodic aluminum oxide by hybrid pulse anodization at

relatively high potential. Electrochem. Solid State Lett.

2004a, 7, B21-B24.

[30] Ono, S.; Saito, M.; Ishiguro, M.; Asoh, H. Controlling

factor of self-ordering of anodic porous alumina. J.

Electrochem. Soc. 2004b, 151, B473-B478.

[31] Nandi, M.; Islam, M.; Mondal, P.; Bhaumik, A. Highly

Efficient Hydroformylation of 1-Hexene over an

ortho-Metallated Rhodium (I) Complex Anchored on a

2D-Hexagonal Mesoporous Material. Eur. J. Inorg. Chem.

2011, 221-227.

[32] Dutta, A.; Mondal, J.; Patra, A. K.; Bhaumik, A.

Synthesis and Temperature-Induced Morphological Control

in a Hybrid Porous Iron-Phosphonate Nanomaterial and Its

Excellent Catalytic Activity in the Synthesis of

Benzimidazoles. Chem. Eur. J. 2012, 18, 13372-13378.

[33] Fan, F. R.; Luo, J. J.; Tang, W.; Li, C. Y.; Zhang, C. P.;

Tian, Z. Q.; Wang, Z. L. Highly transparent and flexible

triboelectric nanogenerators: performance improvements

and fundamental mechanisms. J. Mater. Chem. A 2014, 2,

13219-13225.

[34] Chu, S. Z.; Wada, K.; Inoue, S.; Isogai, M.; Yasumori, A.

Fabrication of Ideally Ordered Nanoporous Alumina Films

and Integrated Alumina Nanotubule Arrays by High-Field

Anodization. Adv. Mater. 2005, 17, 2115-2119.

[35] Schwirn, K.; Lee, W.; Hillebrand, R.; Steinhart, M.;

Nielsch, K.; Gösele, U. Self-ordered anodic aluminum

oxide formed by H2SO4 hard anodization. ACS Nano 2008,

2, 302-310.

[36] Liu, J.; Liu, S.; Zhou, H. H.; Xie, C. J.; Huang, Z. Y.; Fu,

C. P.; Kuang, Y. F. Preparation of self-ordered nanoporous

anodic aluminum oxide membranes by combination of hard

anodization and mild anodization. Thin Solid Films 2014,

552, 75-81.


Nano Res.

Electronic Supplementary Material




Huarui Zhu, 1 Ying Xu, 1 Yu Han, 1 Shuwen Chen, 1 Tao Zhou, 1 Magnus Willander, 1 Xia Cao, 1, 2 () and

Zhonglin Wang, 1, 3 ()

Supporting information to DOI 10.1007/s12274-****-****-*

Figure S1 SEM images of the synthesized mesoporous Al2O3 (a) at higher anodization potentials, (b) the

aluminum oxide without removing thoroughly after the first anodization step.

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Self-powered electrochemical anodic oxidation: A new