&Nanocomposites

Functional Porous Carbon/Nickel Oxide Nanocomposites asBinder-Free Electrodes for Supercapacitors

Rajesh Madhu ,[a] Vediyappan Veeramani ,[a] Shen-Ming Chen,*[a] Pitchaimani Veerakumar,[b]

and Shang-Bin Liu *[b, c]

Abstract: High-surface-area, guava-leaf-derived, heteroatom-containing activated carbon (GHAC) materials were synthe-sized by means of a facile chemical activation method withKOH as activating agent and exploited as catalyst supportsto disperse nickel oxide (NiO) nanocrystals (average size(2.0�0.1) nm) through a hydrothermal process. The texturaland structural properties of these GHAC/NiO nanocompo-sites were characterized by various physicochemical tech-niques, namely, field-emission SEM, high-resolution TEM, ele-

mental analysis, X-ray diffraction, X-ray photoelectron spec-troscopy, thermogravimetric analysis, and Raman spectrosco-py. The as-synthesized GHAC/NiO nanocomposites were em-ployed as binder-free electrodes, which exhibited highspecific capacitance (up to 461 F g¢1 at a current density of2.3 A g¢1) and remarkable cycling stability, which may be at-tributed to the unique properties of GHAC and excellentelectrochemical activity of the highly dispersed NiO nano-crystals.

Introduction

The production of eco-friendly energy-storage devices is im-perative for the development of society. In recent decades, thedevelopment of carbon-based materials for perspective newapplications has drawn considerable research attention.[1–6]

Among them, graphene/metal oxide nanocomposites havebeen widely exploited in various electrochemical applications.In particular, graphene/nickel oxide and graphene/cobalt oxidenanostructures were found to show superior performance insupercapacitor applications.[7–12] In addition to noble and tran-sition metal oxides (or hydroxides), which exhibit high capaci-tance as well as high energy density desirable for supercapaci-tor applications, other mono- and bifunctional metal oxides orhydroxides such as MnO2, NiO/Ni(OH)2, Co3O4/Co(OH)2, Fe2O3,Fe3O4, SnO, V2O5, Bi2O3, MoO2, TiO2, NiCo2O4, NiFe2O4, CoFe2O4,

ZnMnO4, and ZnCo2O4 have also been investigated.[13–15] In thecase of carbon-based materials, preparation of graphene fromgraphite is an intricate procedure that may also lead to hazard-ous explosions. On the other hand, the procedure for fabrica-tion of activated carbons (ACs) from biomass precursors issimple and more environmentally friendly. Moreover, biomass-derived ACs, which have been used in several industrial appli-cations, are known to have unique properties such as ultrahighsurface area, tailorable pore size, low toxicity, good electricalconductivity, high chemical stability, and natural presence ofdesirable surface oxygen functional groups.[1, 16–23]

Nickel oxide nanoparticles (NiO NPs), which have versatilecatalytic activity, have played a critical role in various R&D ef-forts.[24–28] Together with the unique textural properties of thebiomass-derived AC and the prominent changes provoked bythe formation of a nanocomposite between the nickel oxidelayer and carbon sheet, they lead to a variety of nanoscalecrevices to facilitate accessibility of the electrolyte ions to thesurfaces of the electrode. Such carbon/metal oxide composites,which have large redox capacitances, have been extensivelyutilized as efficient electrode materials for alkaline supercapaci-tors.[29–32] Nevertheless, literature reports on utilization of bio-mass-derived ACs for electrochemical applications is rare, andthere is no report available on AC/NiO nanocomposites. Guavaleaves (Psidium guajava), which are rich in lignocellulosic con-tent and easily available worldwide, are desirable biomass re-sources. Moreover, owing to the excellent and unique proper-ties of guava-leaf-derived, heteroatom-containing activatedcarbon (GHAC), we sought to explore the electrochemical per-formance of GHAC/NiO nanocomposites in supercapacitor ap-plications. This was accomplished by assessing their electro-chemical capacitor properties through cyclic voltammetrymeasurements in a three-electrode system. Herein, we report

[a] R. Madhu ,+ V. Veeramani ,+ Prof. Dr. S.-M. ChenElectroanalysis and Bioelectrochemistry LabDepartment of Chemical Engineering and BiotechnologyNational Taipei University of TechnologyTaipei, 10617 (Taiwan)Fax: (+ 886) 2-27025238E-mail : smchen78@ms15.hinet.net

[b] Dr. P. Veerakumar, Prof. Dr. S.-B. LiuInstitute of Atomic and Molecular SciencesAcademia Sinica, Taipei, 10617 (Taiwan)Fax: (+ 886) 2-23620200E-mail : sbliu@sinica.edu.tw

[c] Prof. Dr. S.-B. LiuDepartment of Chemistry, National Taiwan Normal UniversityTaipei 11677 (Taiwan)

[++] These authors contributed equally.

Supporting information for this article is available on the WWW underhttp ://dx.doi.org/10.1002/chem.201500247.

Chem. Eur. J. 2015, 21, 8200 – 8206 Ó 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim8200

Full PaperDOI: 10.1002/chem.201500247

for the first time the synthesis of GHAC/NiO nanocompositesand their applications as efficient binder-free electrodes fornovel supercapacitors, as illustrated in Scheme 1.

Results and Discussion

The morphology of the as-prepared GHAC/NiO samples wasexamined by field emission SEM (FE-SEM). The FE-SEM imagesof the material synthesized by carbonization at 900 8C (GHAC-900, Figure 1 a–c) revealed a honeycomb-like structure withhighly porous morphology. Figure 1 d shows the quantitativeelemental analysis obtained for GHAC-900 by energy dispersiveX-ray (EDX) analysis, revealing the anticipated high carbon con-tent of about 78 wt %. By comparison, the FE-SEM image ofthe as-synthesized GHAC/NiO nanocomposite prepared at900 8C under N2 atmosphere (Figure 2 a) clearly indicates thatthe NiO nanocrystals are evenly embedded in the carbon struc-ture and tend to block the pores of the carbon layers. EDXanalysis (Figure 2 b) confirmed the presence of nickel, carbon,and oxygen in the nanocomposite material.[33] These results in-

dicate that the NiO nanocrystalswere well-dispersed in the GHACmatrix.

Figure 2 c shows the powderXRD patterns of GHACs carbon-ized at different temperaturesand the GHAC/NiO nanocompo-site. All samples exhibited twomain characteristic peaks at 2 q

values of 23.2 and 43.18 corre-sponding to the (002) and (100)index planes, which can be at-tributed to turbostratic andgraphitized carbon, respectively.Additional sharp diffractionpeaks were observed for theGHAC/NiO composite at 2 q

�37.3, 43.3, and 62.98, which correspond to the (111), (200),and (220) planes of the face-centered cubic (fcc) phase of NiO(JCPDS 65-6920), in excellent agreement with the reportedvalues.[34–36] It is noteworthy that only the fcc phase of NiO wasobserved in the GHAC/NiO composite material. Moreover, thedegree of graphitization of various samples was also examinedby Raman spectroscopy, which provides a wealth of informa-tion about their intrinsic carbon structure. As shown in Fig-ure 2 d, all samples showed similar Raman spectra exhibitingtwo broad characteristic peaks centered at 1325 and1589 cm¢1, which can be attributed to the disordered D band(A1g symmetry) and graphitic G band (E2g symmetry) of theideal graphitic lattice, respectively.[37, 38] Moreover, all samplesshowed similar relative peak intensities (IG/ID ratios) indicatingthat their degrees of graphitization are rather similar.

Figure 3 shows high-resolution TEM (HRTEM) images ofGHAC-900 and the GHAC/NiO nanocomposite. In the absenceof NiO, GHAC-900 showed only honeycomb-like mesoscopic

Scheme 1. Schematic synthesis of GHAC/NiO nanocomposites from guava leaves and their application as electro-des for supercapacitors.

Figure 1. a)–c) FE-SEM images and d) elemental data obtained from EDXanalysis of the GHAC-900 sample.

Figure 2. a) FE-SEM image and b) EDX profile of the GHAC/NiO nanocompo-site. c) XRD patterns and d) Raman spectra of various samples.

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amorphous graphitic carbon, whereas the formation of GHAC/NiO nanocomposite can readily be identified by the dark spotsin the TEM image, which can be ascribed to the presence ofNiO nanocrystals (average size (2.0�0.1) nm) uniformly distrib-uted throughout the specimen grid.

The textural properties of GHAC-700, GHAC-800, GHAC-900,and GHAC/NiO composite were determined by measuring N2

adsorption/desorption isotherms at 77 K (Figure 4 a). The ad-sorption/desorption curves exhibited typical type I isothermsaccording to the IUPAC classification, which indicate the coex-istence of micro- and mesoporosity in the GHAC substrate.[39, 40]

The BET surface areas, pore volumes Vtot, and BJH pore sizes(see Figure S1 in the Supporting Information) of various sam-ples are listed in Table 1. In the absence of NiO, consistent in-creases in total surface area Stot and Vtot were observed with in-creasing carbonization temperature of the pristine GHAC. Fur-ther evaluation of the microporosities by t-plot analysis al-lowed the microporous surface areas Smicro and pore volumesVmicro of the GHACs to be determined. This revealed that the in-

creases in Stot and Vtot observed for GHAC with increasing car-bonization temperature were mainly due to the increase inmesoporosity. For example, on raising the carbonization tem-perature from 700 to 900 8C, Smicro and Vmicro remained practical-ly the same, but notable increases in Smeso (from ca. 464 to813 m2 g¢1) and Vmeso (from ca. 0.30 to 0.45 m3 g¢1) occurred.Meanwhile, the pore size also increased from about 2.8 to3.5 nm (see Figure S2 of the Supporting Information andTable 1). However, on incorporation of nickel oxide species,dramatic decreases in both micro- and mesoporosity as well aspore size were evident (see Table 1). This is attributed to block-ing of pores by NiO nanocrystals, as also evidenced by the FE-SEM results (Figure 2 a).

Further quantitative studies on the carbon framework andstability of the GHAC and GHAC/NiO samples were performedby thermogravimetric analysis (TGA) and differential thermalanalysis (DTA) under flowing air. Compared to the GHAC-900sample, which revealed a broad and symmetric TGA-DTA curvein the range of about 500–625 8C (Figure 4 b) due to pyrolysisof the carbon framework.[41] the GHAC/NiO composite exhibit-ed a somewhat asymmetric curve spanning over the range of400–700 8C. The weak weight-loss peak below 100 8C shouldbe due to desorption of physisorbed water. Thus, the thermalanalysis results indicate that the GHAC/NiO composite shouldremain stable up to 400 8C.

Elemental analysis of the GHAC/NiO nanocomposite re-vealed the presence of C (79.14 %), N (1.14 %), S (0.32 %), and H(1.86 %) in the GHAC-900 substrate. As revealed by EDX analy-sis, the other predominant element should be oxygen (pre-sumably >17.5 wt %). It is noteworthy that these activated car-bons derived from an abundant biomass resource (i.e. , guavaleaves) contain heteroatoms that are desirable for enhancingthe electrochemical properties[3–6, 16, 17, 19, 20] of the GHAC/NiOcomposite as prospective electrodes for biosensing and energyapplications. The surface properties of the GHAC/NiO compo-site were further investigated by X-ray photoelectron spectros-copy (XPS, Figure 4 c), which clearly showed the presence ofpredominant species such as C, O, and Ni, whereas no peaksdue to H, N, and S species were visible because of their lowersurface contents. Figure 4 d shows the expanded XP spectrumcovering the Ni 2p1/2 and Ni 2p3/2 regions. The peaks centeredat 860.2 and 868.5 eV correspond to Ni 2p3/2 and Ni 2p1/2 spin

Figure 4. a) N2 adsorption/desorption isotherms. b) TGA profile (inset: DTAcurve) of GHAC-900 and GHAC/NiO. c) XPS profile of GHAC/NiO and d) ex-panded spectrum covering the Ni 2p1/2 and Ni 2p3/2 regions.

Table 1. Textural properties of various as-synthesized samples.

Sample NiO size[nm][a]

Surface area[m2 g¢1][b]

Pore volume[cm3 g¢1][c]

Dp

[nm][f]

IG/ID

Stot Smicro[d] Vtot Vmicro

[d] Vmeso[e]

GHAC-700 – 1005 540.5 0.52 0.22 0.30 2.8 1.2GHAC-800 – 1270 532.3 0.58 0.23 0.35 3.1 1.1GHAC-900 – 1348 535.2 0.69 0.24 0.45 3.5 1.0GHAC/NiO 2.0�0.1 1297 308.4 0.43 0.15 0.28 1.7 1.1

[a] Average NiO crystalline size determined by HRTEM analysis. [b] BETsurface area. [c] Total pore volume calculated at P/P0 = 0.99. [d] Micropo-rous surface area and pore volume obtained from t-plot analysis. [e] Mes-oporous volume (Vmeso = Vtot¢Vmicro). [f] BJH pore diameter determinedfrom the adsorption branch of the isotherm.

Figure 3. HRTEM images of a) GHAC-900 and b)–d) the GHAC/NiO compo-site.

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orbitals (Figure 4 d). The binding energy peaks at about 530.5and 288.0 eV correspond to O 1s and C 1s, respectively (Fig-ure 4 c).[42, 43]

Figure 5 a shows the cyclic voltammograms (CVs) of NiO-freeGHAC-700, GHAC-800, and GHAC-900 samples at a fixed scanrate of 7 mV s¢1 in 1 m KOH electrolyte. Interestingly, all electro-

des showed the typical rectangular shape corresponding tothe redox properties of the surface oxygen functional groupsduring the charge/discharge process. At a constant scan rateof 7 mV s¢1, the specific capacitances calculated for GHAC-700,GHAC-800, and GHAC-900 were 27, 33, and 66 F g¢1, respec-tively, which suggest an increase in specific capacitance withincreasing cabonization temperature of the GHAC. The largercurrent area observed for the GHAC-900 electrode comparedto its NiO-free counterparts revealed an increase in storage ca-pacitance with increasing carbonization temperature of theGHAC. Moreover, the CV curves observed for the fabricatedelectrodes (Figure 5 b) maintained the nearly rectangular shapeeven at varied scan rates (2–30 mV s¢1). This indicates that, inaqueous alkaline solution (1.0 m KOH), capacitance can bestored at the electrode/electrolyte interfaces through accumu-lation of electrolyte ions. The excellent electrochemical reversi-bility may be attributed to the pseudocapacitive contributionarising from the surface oxygen functional groups,[44] whichhave been shown to improve wettability of the substrate andmaximize the electroactive surface area.[45] Figure 5 c shows thegalvanostatic charge/discharge (GCD) curves of the GHAC-900electrode at varied current densities. Accordingly, specific ca-pacitances of 55, 58, 60, 61, 62.5, and 66 F g¢1 can be deducedfor the GHAC-900 electrode at current densities of 10, 5, 3, 2,1.5, and 1 A g¢1, respectively. For comparison, the electrochem-ical performances and GCD properties of GHAC-700 and

GHAC-800 electrodes are shown in Figure S2 in the SupportingInformation. In general, GHAC carbonized at higher tempera-tures shows a higher specific capacitance. In this context, be-sides the presence of heteroatoms in GHAC electrodes, samplesurface area and pore volume are also crucial components inobtaining a desirable supercapacitor performance.

The stability of the GHAC-900 electrode was further exam-ined by cyclic measurements. As shown in Figure 5 d, the ob-served specific capacitance of the binder-free GHAC-900 elec-trode decreased only by about 6.7 % of its initial capacitanceeven after 2500 charge/discharge cycles. The excellent stabilityobserved for the GHAC electrode is attributed to its uniquetextural and electrochemical properties (see above), whichtend to promote intercalation and de-intercalation processesof the electrochemical species after some initial cycles.[46]

Moreover, the electrochemical performance of the as-pre-pared GHAC/NiO nanocomposite was also assessed and com-pared to that of bare NiO. Figure 6 a shows the CV curves of

NiO and GHAC/NiO nanocomposite recorded at a scan rate of10 mV s¢1 in 1 m KOH aqueous electrolyte solution. Clearly,a much higher redox peak current area was observed forGHAC/NiO than for bare NiO and indicates much higher specif-ic capacitance of the nanocomposite material. Moreover, thefact that the redox peak current observed for the GHAC/NiO

Figure 5. CV curves of a) various GHAC electrodes recorded by usinga three-electrode system in 1.0 m KOH aqueous electrolyte at a fixed scanrate of 7 mV s¢1 and b) the GHAC-900 electrode recorded at various scanrates. c) Variations of GCD curves with current density and d) cyclic per-formance of the GHAC-900 electrode measured at a constant current densityof 3.0 A g¢1 (inset: variation of potential with time during charge/dischargecycles).

Figure 6. CV curves of a) NiO and GHAC/NiO electrodes recorded at a fixedscan rate of 10 mV s¢1 and b) GHAC/NiO recorded at various scan rates in1 m KOH electrolyte. GCD curves of c) NiO and d) GHAC/NiO electrodes atvarious current densities, their corresponding e) variations of specific capaci-tance with current density, and f) comparison of cyclic performances mea-sured at a current density of 4.6 A g¢1 (insets: corresponding variations ofpotential versus time during charge/discharge cycles).

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electrode increases with increasing scan rate (Figure 6 b) ruledout a surface-controlled process.

On the basis of the charge/discharge results obtained forNiO and GHAC/NiO electrodes at various current densities (Fig-ure 6 c and d, respectively), their corresponding variations ofspecific capacitance with current density are depicted in Fig-ure 6 e. Clearly, the binder-free GHAC/NiO nanocomposite elec-trode showed much higher specific capacitance than unsup-ported NiO and bare GHAC-900. For example, at a constantcurrent density of 3.0 A g¢1, the specific capacitances derivedfor GHAC-900, NiO, and GHAC/NiO electrodes were 60, 200,and 361 F g¢1, respectively. In other words, the specific capaci-tance dramatically increased sixfold on incorporating about0.3 wt % of NiO nanocrystals into the GHAC support. Moreover,as evidenced in Figure 6 f, excellent electrochemical stabilitywas also observed for the GHAC/NiO electrode; about 83 % ofits initial capacitance was retained even after consecutivecharge/discharge operations up to 1000 cycles, comparable toother modified electrodes reported in the literature (see Sup-porting Information, Table S1).[9, 47–50]

Finally, electrochemical impedance analysis was performedto explore the charge-transfer behavior at the electrode/elec-trolyte interface. Electrochemical impedance spectroscopy wascarried out in the frequency range between 0.1 and 10 MHzwith a perturbation-potential amplitude of 10 mV. The Nyquistplots obtained from GHAC and GHAC/NiO samples (Figure 7)

all show a single semicircle in the mid-frequency region ac-companied by a spike (or tail) in the low-frequency region. Thelatter most likely arises from the capacitive behavior of theelectrode material. In general, the intersection of semicircle inthe high-frequency region represents the equivalent series re-sistance (ESR), which is a combination of solution resistance,the intrinsic resistance of the active material, and interfacial re-sistance at the active material and current collector. In thiscase, the ESR value is nearly the same for all samples. On theother hand, the diameter of the semicircle represents thecharge-transfer resistance at the electrode/electrolyte interface.GHAC/NiO exhibited a lower charge-transfer resistance thanGHAC, most likely due to a synergistic effect between the indi-vidual components.[51] Thus, the binder-free GHAC/NiO nano-composite reported hierein, which can be facilely prepared inbulk quantities from biomass resources, is a novel cost-effec-tive electrode material for prospective new applications inhigh-performance supercapactiors.

Conclusion

We have reported the synthesis of GHAC/NiO nanocompositematerials using a simple, eco-friendly method. Such nanocom-posite materials show remarkable performance as binder-freeelectrodes in supercapacitor applications. The superior electro-chemical activity observed for GHAC/NiO can be attributed tothe catalytic activity of the NiO nanocrystals as well as thehigh surface area of and presence of heteroatom species inthe biomass-derived GHAC support, which enhance the surfacewettability and induce pseudocapacitive behavior that is favor-able for high-performance supercapacitor applications.

Experimental Section

Preparation of GHAC/NiO nanocomposites

GHAC materials with unique textural properties containing heter-oatoms and surface functional groups were prepared by a simpleand eco-friendly chemical activation method by using guava leaves(Psidium guajava) as the carbon precursor. Typically, the driedguava leaves were first pulverized and preheated at 100 8C for 2 d.Then, a desired amount of the preheated sample was activated at60 8C in 10 % KOH for 24 h under stirring in an N2 atmosphere. Sub-sequently, the activated sample was carbonized in a tube furnaceat different temperatures (700, 800, and 900 8C) for 2 h in N2 at-mosphere with a heating rate of 5 8C min¢1. Finally, the carbonizedGHAC powder was washed with hot distilled water and 1 m HCl toremove KOH and other impurities, followed by drying at 150 8Covernight before being ground to fine powder. The activatedcarbon samples thus obtained are denoted as GHAC-x, where rep-resents the carbonization temperature in 8C.

The GHAC/NiO nanocomposite was prepared by a simple hydro-thermal method. Typically, about 100 mg of GHAC-900 was dis-persed in 50 mL of an ethanol/water (1/1, v/v) solution containingcetyltrimethylammonium bromide (0.1 g) and 0.05 mNi(NO3)2·6 H2O. The solution was sonication for 1–2 h, and then anappropriate amount of liquid ammonia solution (25 wt %) wasslowly added to this suspension, which was stirred for an addition-al 2–3 h. The suspension was sealed in a 100 mL Teflon-lined stain-less steel autoclave for hydrothermal reaction at 100 8C for 10 h.The product was collected by centrifugation, washed with deion-ized water and then ethanol, and dried at 80 8C in air for 12 h. Thesamples were heated to 350 8C, and then the temperature wasraised to 900 8C for 3 h under an N2 atmosphere to obtain the finalGHAC/NiO nanocomposite sample.

Electrode preparation

For supercapacitor applications, a GHAC/NiO electrode was pre-pared by mixing GHAC-900 (85 wt %) and graphite (15 wt %) with0.4 mL of N-methylpyrrolidone to form a homogeneous slurry.Then, ca. 15 mL of the above slurry was coated on a stainless steelelectrode with dimensions of about 1 Õ 1 cm2 by a solution-castingmethod, followed by drying overnight at 60 8C. The mass loadingof GHAC-900 on the substrate was about 1.3 mg cm¢2. Prior toelectrochemical studies, the cell was soaked in electrolyte for a fewhours. The electrochemical properties of the cell were examined inthe potential range of ¢1.0 to 0 V by using a CV apparatus. Thebinder-free GHAC/NiO/stainless steel electrode thus prepared wasused for further electrochemical experiments at room temperatureunder an inert atmosphere.

Figure 7. Nyquist plots for GHAC and GHAC/NiO.

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Electrochemical studies

Electrochemical properties of various GHAC and GHAC/NiO electro-des were assessed by using a three-electrode system in 1.0 m KOHaqueous electrolyte solution. The three-electrode system consistedof GHAC or GHAC/NiO as the working electrode, Ag/AgCl as thereference electrode, and a platinum wire as the counter electrode.All CV and galvanostatic charge/discharge (GCD) experiments wereperformed on an electrochemical work station (CHI627). The specif-ic capacitances of the sample electrodes were calculated by usingEquation (1) for CV measurements[46]

C ¼ Q=mDV ð1Þ

where C is the specific capacitance in units of F g¢1, Q the averagecharge during the charge and discharge process (in units of C), mis mass of the active material in units of g, and DV the working po-tential in units of V, and Equation (2) in the case of GCD measure-ments

C ¼ IDt=mDV ð2Þ

where I is the applied current density in units of A and Dt thecharge/discharge duration in units of s.

Physicochemical characterization

Samples were characterized by various physicochemical tech-niques. XRD studies were carried out on a Rigaku (MiniFlex II) dif-fractometer. Raman spectra were recorded on a WITeck CRM200confocal Raman microscopy system with a 488 nm laser. The mor-phology of various samples was examined by FE-SEM (JEOL, JSM-6700F), and FE-TEM (JEOL, JEM-3000F) at 300 kV. For XPS anULVAC-PHI PHI 5000 VersaProbe equipment was used. N2 adsorp-tion/desorption isotherms were studied by using a QuantachromeAutosorb-1 physisorption system. TGA and DTA were performedon a Netzsch TG-209 instrument under air atmosphere.

Acknowledgements

Financial supports of this work by the Ministry of Science andTechnology, Taiwan (NSC101-2113M-027-001-MY3 to S.-M.C. ;NSC101-2113M-001-020-MY3 to S.-B.L.) are gratefully acknowl-edged. The authors thank Mr. Rajkumar Madhu (Department ofEnglish (MCAS), Periyar University, India) for help with betterlanguage proficiency and collection of biomass samples.

Keywords: biomass · carbon · electrochemistry ·nanostructures · nickel

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Received: January 19, 2015

Published online on April 16, 2015

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