Nanostructured carbon-metal hybrid aerogels from bacterial cellulose

Bernd Wickleina,*, Judith Arranza, Alvaro Mayoralb, Pilar Arandaa, Yves Huttela, Eduardo Ruiz-Hitzkya

aInstituto de Ciencia de Materiales de Madrid, CSIC, c/ Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain

b Laboratorio de Microscopías Avanzadas, Instituto de Nanociencia de Aragón, Universidad de Zaragoza, c/ Mariano Esquillor, Edificio I+D,

50018, Zaragoza, Spain

*Author for correspondence. E-mail: bernd@icmm.csic.es

Figure S1: Experimental procedure for the synthesis of carbon-nickel (C-Ni) from pyrolysis of BC-Ni(OH)2.

Electronic Supplementary Material (ESI) for RSC Advances.This journal is © The Royal Society of Chemistry 2017

Figure S2: Particle size distribution from STEM image analysis and fitted with a Gaussian distribution function (A). The center of the distribution is 8.6 nm and the FWHM is 9.0 nm. An exemplary Cs-corrected STEM image of Ni@NiO nanoparticles, which was used for size distribution analysis (B).

0.0 0.2 0.4 0.6 0.8 1.00

50

100

150

200

adsorption desorption

Qua

ntity

ads

orbe

d (c

m3 /g

STP

)

Relative pressure (p/po)

Figure S3 N2 adsorption isotherm of C-Ni

Figure S4. Ni 2p core level XPS spectrum of C-Ni shows three contributions at 852.4 eV, 855.1 eV and 860.8 eV binding energy, which can be attributed to metallic Ni, NiO, and NiOH, respectively [1] (A). Cs-corrected STEM micrograph and the corresponding EEL spectrum images (i,ii,iii) across a Ni@NiO nanoparticle (B). Color code: red refers to Ni-L3,2 and green to O-K edges. EEL spectrum image i is an overlay of ii and iii. O 1s core level XPS spectrum of C-Ni showing a component located at 531.2 eV that has been attributed to crystal defects within the oxide [2] (C).

0 200 400 600 8000

20

40

60

80

100

315C, 10%

260C, 20%340C, 65%

380C, 17%

35%

Wei

ght (

%)

Temperature (C)

BC BC-Ni(OH)2

22%

Figure S5. Thermogravimetric curves of BC and BC-Ni(OH)2 in nitrogen.

5 nm 5 nm

Figure S6. Cs-corrected TEM-BF micrographs of C-Ni showing Ni@NiO NPs covered by disordered graphite layers as suggested by the increased d(001) spacing of 42-46 Å (A). The NPs are embedded in a matrix of amorphous carbon (B).

500 1000 1500 2000 2500 3000

G

2D

C-Ni

Inte

nsity

(a.u

.)

Raman shift (cm-1)

D

Figure S7. Raman spectrum of C-Ni showing the absence of the graphene 2D band at

~2700 cm-1. The Raman spectrum was smoothed applying the Savitzky-Golay method

with a 2nd polynomial order and 67 points of window.

4000 3500 3000 2500 2000 1500 1000 500

OH

C=O

Ni-O

C-OHC=C

3060

3460

440

8531192

13821460

1723

Inte

nsity

(a.u

.)

Wavenumber (cm-1)

C-Ni

1657C=C

Figure S8. FTIR spectrum of C-Ni. The presence of functional carbon oxygen groups, i.e. C-O (1382 cm-1) and C=O (1723 cm-1), is observed together with indications of aromatic C=C groups (1460 cm-1).

100 200 300 400 500

1E-3

0.01

0.1

100 200 300 400 500

Io

n cu

rrent

(nA)

Temperature (C)

15 30 42 56 58 60 68

0.001

Temperature (C)

Figure S9. TG-MS curves of BC-Ni(OH)2 (A) and BC (B) recorded in N2 atmosphere. The curves correspond to ionized species with mass-to-charge ratios m/z of 15 (methyl); 30 (ethane); 42 (propene/ketene); 56 (2-propenal); 58 (ethanedione/propanone); 60 (acetic acid); 68 (furan). Species of m/z>68 did not evolve in significant quantity and remained below the quantity of furan.

In bacterial cellulose alone the decomposition products are generated in one

temperature region around 325 °C, while in BC-Ni(OH)2 at 260 °C and 340 °C.

Interestingly, in the presence of Ni(OH)2 the cellulose decomposition occurs about 70

°C below the decomposition temperature of pure bacterial cellulose. It is well-known

that nickel compounds can catalyze the thermal decomposition of cellulose and other

biomass and reduce the decomposition temperature [3,4].

Figure S10: TG-MS curves of CO (A) and CO2 (B) evolved from BC-Ni(OH)2 under nitrogen. The green curves are Gaussian fits and the red curves are the envelope.

Figure S11: XRD pattern of Ni and a Ni/NiO mixture as obtained by carbothermal reduction of BC-Ni(OH)2 and glucose-Ni(OH)2, respectively.

Figure S12: Photographs of a BC cube with infiltrated FeCl3 (left) and the same cube

after immersion in 1M NaOH for one hour (right), which provoked the precipitation of

FeO(OH) within the BC cube.

100 200 300 400 500 600 700

-20

-10

0

40

60

80

100

He

at fl

ow (m

W)

Temperature (C)

225

W

eigh

t (%

)

641

4199557

Figure S13: TG and DSC curves of BC-Fe(OH)3 obtained under nitrogen atmosphere. The DSC peak at 641 °C can be attributed to the reduction of iron oxide to metallic Fe.

0 100 200 3000

2

4

6

8

10

FC

M (e

mu

/ gN

i)

Temperature (K)

ZFC

Figure S14: Plots of Zero Field Cooling (ZFC) – Field Cooling (FC) runs of the magnetization versus temperature, M(T), as measured under 50k Oe cooling field and 50 Oe measuring field.

The ZFC and FC curves are widely separated from each other, which is a strong

indication for magnetic anisotropy of the ferromagnetic phase. Furthermore, the

blocking temperature, TB, that is the transition from a magnetically blocked state to a

superparamagnetic state, appears to be above 300 K as the ZFC curve does not show

any peak in the measured temperature range. This behavior can be related to the

broad particles size distribution as observed in the TEM investigations and therefore,

the superparamagnetic effect typically observed for Ni nanoparticles, is absent in C-Ni.

References

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Hydrogen Energy 2016, 41, 8656–8667.

[4] C. Wu, Z. Wang, J. Huang, P. T. Williams, Fuel 2013, 106, 697–706.