C A R B O N 5 0 ( 2 0 1 2 ) 3 0 3 2 – 3 0 3 8

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Graphene growth on nanodiamond as a support for a Ptelectrocatalyst in methanol electro-oxidation

Jianbing Zang a,b, Yanhui Wang a,*, Linyan Bian a, Jinhui Zhang a, Fanwei Meng a,Yuling Zhao a, Rui Lu a, Xuanhui Qu b, Shubin Ren b

a State Key Laboratory of Metastable Material Science & Technology, College of Material Science & Engineering, Yanshan University,

Qinhuangdao 066004, PR Chinab State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology

Beijing, Beijing 100083, PR China

A R T I C L E I N F O

Article history:

Received 16 December 2011

Accepted 28 February 2012

Available online 7 March 2012

0008-6223/$ - see front matter � 2012 Elsevihttp://dx.doi.org/10.1016/j.carbon.2012.02.089

* Corresponding author: Fax: +86 335 8387679E-mail address: diamond_wangyanhui@1

A B S T R A C T

A core/shell structure nanodiamond/graphene (ND/G) was prepared by annealing ND in a

vacuum at the temperatures of 1200 and 1500 �C. ND/G with a controllable few-layer graph-

ene covering on the ND surface was achieved. The prepared ND/G was used as a support for

a platinum (Pt) electrocatalyst in direct methanol fuel cells. A higher dispersion of Pt nano-

particles was observed on ND/G compared to pristine NDs and the material showed better

catalytic activity and greater stability for methanol electro-oxidation than Pt/ND.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

Graphene, a 2D honeycomb lattice of sp2-bonded carbon

atoms, has attracted tremendous attention in recent years be-

cause of its fascinating properties [1,2]. It has become a novel

and very promising material in many fields, such as nano-elec-

tronics [3], composite materials [4], chemical sensors [5], and

energy storage and conversion [6,7]. Especially, graphene has

a potential application as a heterogeneous catalyst support in

direct methanol fuel cells (DMFCs) due to its considerable

surface area and exceptionally high electrical conductivity [8–

10]. However, monolayeric graphene tends to form irreversible

agglomerates or can even restack to form graphite through van

der Waals interactions during the processing and application

of bulk-quantity graphene. Moreover, amongst the reported

methods, chemical exfoliation is considered to be an efficient

approach to produce graphene sheets in large volumes [11–

13]. However, the prepared graphite oxide nanosheets require

severe chemical and thermal reductive treatments for practical

applications. These severely restrict the applications of graph-

ene. In addition, it is difficult for the electrolyte to penetrate

er Ltd. All rights reserved

.63.com (Y. Wang).

into the basal layers when graphene nanosheets are used as

electrodes in electrochemical fields. The incorporation of car-

bon nanoparticles, such as carbon black [14] or carbon nano-

tubes [15,16] into graphene layers, can increase the distance

between the graphene sheets, and consequently inhibit the

agglomeration of graphene and improve electrolyte–electrode

accessibility.

In this paper, we prepared a nanodiamond/graphene (ND/

G) composite with a diamond core covered by a graphene

shell, and used ND/G as a support material for the dispersion

of platinum (Pt) nanoparticles to develop advanced electrocat-

alyst materials for DMFCs. Recently, ND particles synthesised

by detonation (�5 nm) or by mechanical milling (50–100 nm)

have been applied in the electrochemical field as an electrode

material [17–20]. They also have great potential for use as a

catalyst support for DMFCs because of their enormous specific

surface area and high thermal and chemical stabilities [20,21].

In this study, NDs with the size of �50 nm prepared by milling

microdiamonds were annealed in a vacuum in the tempera-

ture range of 1200–1500 �C. Surface graphitisation led to the

formation of a layered graphene shell on the ND surface.

.

C A R B O N 5 0 ( 2 0 1 2 ) 3 0 3 2 – 3 0 3 8 3033

The shell endowed ND/G with high conductivity and a high

affinity for the catalyst metal, while the diamond core re-

tained high thermal stability and morphological stability un-

der oxidising conditions, which is necessary for the

durability of DMFCs [22]. The graphene layers, separated by

the diamond cores as stiff spacers, overcome the self-aggrega-

tion between the large and planar basal planes in pristine

graphene sheets. ND/G with a high surface area and a non-

porous and fully accessible surface is expected to have high re-

sponse rates. So, it is a potential excellent catalyst support for

methanol oxidation. Moreover, the reduction process, which is

necessary for graphene oxide, can be omitted for graphene

layers directly derived from diamond.

500 1000 1500 2000 2500 3000

1344

2684

1588

Inte

nsity

Raman shift (cm-1)

GND-1200 GND-1500 ND

1325

Fig. 1 – Raman spectra of the ND and ND/G prepared in a

10�3 Pa vacuum at the temperatures of 1200 �C (ND/G-1200)

and 1500 �C (ND/G-1500).

2. Experimental

ND powders produced by milling microdiamonds were sup-

plied by Element Six Ltd. The average size of the particles

was about 50 nm. To obtain core/shell structural ND/G,

annealing was carried out in a 10�3 Pa vacuum at the temper-

atures of 1200–1500 �C for 1 h; the samples were defined as

ND/G-1200 and ND/G-1500, respectively.

The phase structure was identified by means of Raman

spectra and X-ray diffraction (XRD). Raman analysis was per-

formed using a Renishaw inVia Raman microscope using the

514 nm line from an Ar ion laser. XRD measurements were

carried out using a D/Max-2500pc diffractometer equipped

with a standard Cu-Ka radiation source. Particle morphology

was observed using a Hitachi H2120 transmission electron

microscope. The specific surface areas were determined by

the BET measurement (NOVA 4200-P, US).

A platinum precursor (H2PtCl6Æ6H2O), ethylene glycol (EG),

and sulphuric acid (H2SO4) were purchased from Shanghai

Chemical Products Ltd. Deionised water was used to prepare

the solutions and high-purity nitrogen gas was also used in

the experiments.

In a typical procedure, an aqueous H2PtCl6 solution

(2.0 mL, 0.055 M) was mixed with EG (25 mL) in a 100 mL bea-

ker. The mixture was uniformly mixed with ND/G powder

(20 mg) using ultrasound. The beaker was placed in the centre

of a microwave oven and heated for 80 s at 800 W. The result-

ing suspension was filtered and the residue was washed with

acetone and deionised water. The solid products were dried at

100 �C for 12 h in a vacuum oven.

The prepared Pt/ND/G were characterised by the methods

of transmission electron microscopy (TEM) and XRD analysis.

The electrochemical experiments were performed on a

CHI660A electrochemistry analyser. Ten milligrams of Pt/

ND/G powder were mixed with distilled water and a Nafion

(20% Nafion and 80% EG) solution under sonication for

20 min. One drop of the slurry was cast on a glass carbon

(GC) electrode (2 cm in diameter) and dried at 80 �C to prepare

the Pt/ND/G/GC electrode. A conventional three-electrode

system was used, consisting of a Pt/ND/G/GC electrode as

the working electrode, a platinum coil auxiliary electrode

and an Ag/AgCl electrode as the reference electrode. Cyclic

voltammograms (CVs) in H2SO4 aqueous solution were re-

corded. Methanol oxidation was studied in a 0.5 M H2SO4

solution containing 1.0 M methanol. In order to investigate

the electrochemical oxidation of the supports, the CVs of

ND/G-1200 and ND were measured between 0 and 1.2 V in

0.5 M H2SO4 for 500 cycles.

3. Results and discussion

3.1. Characteristics of ND/G composite

Raman spectra were obtained to investigate the surface gra-

phitic structure of ND before and after vacuum annealing at

the different temperatures, as shown in Fig. 1. The Raman

spectrum of the pristine ND in Fig. 1 exhibited a peak centred

at 1325 cm�1, associated with a diamond sp3 bonding scheme.

A small peak around 1610 cm�1 was assigned to sp2 defects

on the ND surface [23]. It was clear that the ND powder pro-

duced by milling high-pressure synthetic microdiamonds

was relatively free of graphite-like sp2 bonded carbon. The

peak at 1325 cm�1 decreased with increased annealing tem-

perature, and a peak centred at 1588 cm�1 was seen after vac-

uum annealing at 1200 �C, indicating the presence of the

graphitic G band. The corresponding graphitic G 0 band at

2684 cm�1 and D band at 1344 cm�1 [24] were also observed

after vacuum annealing at 1500 �C. This suggested that a sur-

face graphene layer was obtained when the sample was an-

nealed in a vacuum.

Fig. 2 shows the morphology of the pristine ND (a) and ND/

G-1500 (b) powders. The ND particles produced by milling ex-

hibit pronounced facets as they originated from splitting lar-

ger crystals along their lattice planes ( Fig. 2a). Annealing

treatment at 1500 �C did not lead to a change in the shape

of the particles, but a shell formed on the surface (Fig. 2b).

Fig. 3 shows the high-resolution TEM (HRTEM) images of ND

(a), ND/G-1200 (b), and ND/G-1500 (c). The straight lines with

spacing of 0.206 nm in Fig. 3a corresponded to the diamond

(111) planes. No indication of a surface graphitic layer was

found on the pristine NDs. This was consistent with the Ra-

man results. The dark lines with wider spacing (0.333 nm)

which appear in Fig. 3b and c indicate surface ‘‘graphitisation’’

after annealing at 1200 �C. A thin graphene shell with two to

three graphite layers formed on the ND surface parallel to

Fig. 2 – TEM images of the pristine ND (a) and ND/G-1500 (b).

Fig. 3 – HRTEM images of ND (a), ND/G-1200 (b) and ND/G-1500 (c). The inset in (b) is a magnification of the interface, in which

the unit is nm.

3034 C A R B O N 5 0 ( 2 0 1 2 ) 3 0 3 2 – 3 0 3 8

the (111) plane of diamond. As the annealing temperature in-

creased, the shell thickened, and the layer number increased.

A successive graphene shell containing 10–14 layers covered a

diamond core after vacuum annealing at 1500 �C. The dis-

tance between the atomic layers of graphene and diamond

could be determined from the HRTEM as shown in the inset

in Fig. 3b. It was found that the interlayer distance gradually

increased from 0.206 nm in the diamond crystals to

0.333 nm in the graphene shells. Interface layers with a dis-

tance less than 0.333 nm were observed, indicating an inter-

action between the diamond and graphene layers.

In order to investigate the electrochemical oxidation of

ND/G and ND as supports, the CVs of ND/G and ND were re-

corded in 0.5 M H2SO4 before and after 500 cycles between 0

and 1.2 V, as shown in Fig. 4. For typical sp2 carbon materials,

increased area of the electrochemical characteristic curve

indicates deteriorated stability of the support due to remark-

able changes in the surface or chemical states. So, an in-

creased area difference before and after cycling is often

used as a criterion of the stability of supports [25,26]. In both

Fig. 4a or b, there is little variation in the area of CVs before

and after 500 cycles, indicating that both ND/G-1200 and ND

0 20 40 60 80 100

0

1000

2000

3000

4000

5000

ND/G-1500

DiamondDiamond

2θ (°)

Graphite

0500

10001500200025003000

Inte

nsity

(a.u

.)

Diamond

PtPtPtPt

Diamond

Diamond

Diamond

Graphite

PtPt/ND/G-1500

Fig. 5 – XRD patterns of ND/G-1500 and Pt/ND/G-1500.

0.0 0.2 0.4 0.6 0.8 1.0 1.2-0.02

-0.01

0.00

0.01

0.02C

urre

nt/ m

A

Potential/ V

1st cycle 100th cycle 500th cycle

a

0.0 0.2 0.4 0.6 0.8 1.0 1.2-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

500th cycle

Cur

rent

/ mA

Potential/ V

1st cycle

100th cycle

b

0.0 0.2 0.4 0.6 0.8 1.0 1.2-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

Cur

rent

/ mA

Potential/ V

1st cycle 100th cycle 500th cycle

c

Fig. 4 – CVs in 0.5 M H2SO4 before and after 500 cycles

between 0 and 1.2 V, v = 0.05 V s�1 vs. Ag/AgCl. (a) ND, (b)

ND/G-1200 and (c) ND/G-1500.

C A R B O N 5 0 ( 2 0 1 2 ) 3 0 3 2 – 3 0 3 8 3035

were highly resistant to electrochemical oxidation. In Fig. 4c,

two small peaks presented at 0.43 and 1.07 V at the first cycle,

and a small area difference of the CV curves was observed

after 100–500 cycles, suggesting slight oxidation of the thick

graphite layer. It is also noted that the background currents

of the ND/G-1200 and ND/G-1500 electrodes in 0.5 M H2SO4

were one order magnitude greater than the ND electrode be-

cause of the formation of the graphene shell. The above re-

sults indicate that ND/G had higher conductivity than ND

and simultaneously retained high electrochemical stability.

3.2. Characteristics of Pt/ND/G

Platinum nanoparticles supported on ND/G powder were pre-

pared by microwave-assisted reduction. Microwave heating is

a rapid, uniform, and effective heating method, and thus is

widely used to synthesise nano-sized Pt catalysts supported

on carbon supports [27–30]. Fig. 5 shows the XRD patterns of

ND/G-1500 and Pt/ND/G-1500. The peaks appeared at 2h val-

ues of 43.98�, 75.28�, and 91.68� corresponding to the (111),

(220), and (311) cubic diamond planes. The wide peak around

26.3� confirmed the presence of the graphene layer on ND

after vacuum annealing. The peaks with the 2h values of

39.8�, 46.2�, 67.4�, 81.2�, and 85.7� corresponded to the reflec-

tion planes (111), (200), (220), (311), and (222) of the cubic

Pt crystals, respectively. This confirmed the presence of crys-

talline Pt nanoparticles on the ND/G support. The widening of

the peaks indicated the nano-scale of the Pt particles.

Fig. 6 shows the TEM images of Pt/ND (a) and Pt/ND/G-1200

(b) prepared by the microwave polyol process. Fig. 6c and d are

the Pt particle size distributions corresponded to Fig. 6a and b,

which are a statistical evaluation determined from a number

of TEM images. Platinum particles with a size of 3–5 nm were

deposited on ND and ND/G supports. It was found that more

homogeneous nanoparticles dispersed on ND/G-1200 (Fig. 6d)

than on the ND support (Fig. 6c). The higher dispersion of the

Pt particles may have been due to a higher affinity of the Pt

metal for the graphene layer compared to diamond, with con-

sequently more nucleation sites [31]. From the HRTEM image

in Fig. 6e, the nanoparticles were identified as face-centred

cubic metal Pt with a lattice parameter of 0.227 nm

(corresponding to the (111) facet).

3.3. Electrochemical properties of Pt/ND/G catalysts

The CVs of the Pt/ND/GC, Pt/ND/G-1200/GC, and Pt/ND/G-1500/

GC electrodes in a 0.5 M H2SO4 aqueous solution were recorded

vs. Ag/AgCl, as shown in Fig. 7a. In the cathode region, they all

displayed the well-known characteristic peaks of bulk Pt elec-

trodes. The active specific surface area of Pt particles for cata-

lysts can be determined by the integrated charge in the

hydrogen adsorption region of the CVs [32,33]. The areas in

m2 g�1 were calculated from the following formula [34]:

Perc

enta

ge (%

)

Pt particle size (nm)

c

1 2 3 4 5 6 7 80

5

10

15

20

25

30

35

40

1 2 3 4 5 6 7 80

5

10

15

20

25

30

35

40

Perc

enta

ge (%

)

Pt particle size (nm)

d

b

0.206nm

0.227nm

e

a

Fig. 6 – TEM images of Pt/ND (a) and Pt/ND/G-1200 (b), their histograms of the Pt size distribution (c, d), and HRTEM image of

Pt/ND/G-1200 (e).

3036 C A R B O N 5 0 ( 2 0 1 2 ) 3 0 3 2 – 3 0 3 8

SEL ðm2=g PtÞ ¼ QH=ðQref � Pt loadingÞ ð1Þ

where SEL is the active specific surface area of the electro-

chemically obtained Pt particles and QH represents the num-

ber of Pt sites available for hydrogen adsorption/desorption

(mC cm�2). Qref = 0.21 mC cm�2 is generally accepted for poly-

crystalline Pt electrodes. The SEL values were obtained as

137.9 m2 g�1 for Pt/ND/G-1500 and 125.1 m2 g�1 for Pt/ND/G-

1200, while SEL = 96.2 m2 g�1 was found for Pt/ND. The specific

surface area of the NDs determined by BET measurement was

81.6 m2 g�1, and the values of ND/G-1200 and ND/G-1500 were

84.2 and 83.5 m2 g�1, respectively. The slight surface area

difference of the supports should not result in a distinct in-

crease in the active specific surface area of Pt particles on

ND/G support. It was attributed to higher affinity for Pt metal

with ND/G than with ND and consequent high dispersity of Pt

particles on ND/G support.

Fig. 7b shows the CVs of Pt/ND/GC, Pt/ND/G-1200/GC, and

Pt/ND/G-1500/GC electrodes in 1.0 M CH3OH + 0.5 M H2SO4

aqueous solutions. Two peaks of methanol oxidation were

seen at 0.62 and 0.43 V, respectively. The starting oxidation

potentials of the Pt/ND/G-1200/GC and Pt/ND/G-1500/GC elec-

trodes moved in a more negative direction, and the oxidation

currents were distinctly higher than that of the Pt/ND/GC

electrode. The mass activity was defined as peak current den-

sity obtained on the CVs at 0.02 V s�1 (Fig. 6b) per unit of Pt

loading mass. The values were estimated to be 98.7 and

91.1 A g�1 for Pt/ND/G-1500 and Pt/ND/G-1200, respectively,

while only 28.8 A g�1 was found for Pt/ND. All these results

confirmed the better catalytic activity of Pt/ND/G/GC in com-

parison to Pt/ND/GC.

The chronoamperometry profiles of methanol electro-oxi-

dation at 0.62 V in Fig. 7c shows that the currents of methanol

electro-oxidation over the catalysts decreased moderately

with time because the intermediate products of methanol

oxidisation, such as CO and other ions in the electrolyte, were

adsorbed onto the Pt nanoparticles, and inhibited the reac-

tion. It also showed that the Pt/ND/G-1200 catalysts exhibited

-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Cur

rent

(mA)

Potential (V)

Pt/ND/G-1500/GC Pt/ND/G-1200/GC Pt/ND/GC

a

0.0 0.2 0.4 0.6 0.8 1.0-1

0

1

2

3

4

5

6b

Cur

rent

(mA)

Potential (V)

Pt/ND/G-1500/GC Pt/ND/G-1200/GC Pt/ND/GC

0 100 200 300 400 500 6000

2

4

6

8

10

12

14

16

18

20

Cur

rent

(mA)

Time (s)

Pt/ND/G-1200/GC Pt/ND/G-1500/GC Pt/ND/GC

c

Fig. 7 – Electrochemical properties of Pt/ND and Pt/ND/G vs.

Ag/AgCl. (a) CVs in an H2SO4 electrolyte, v = 0.05 V s�1, (b)

CVs in a 1.0 M CH3OH + 0.5 M H2SO4 solution, v = 0.02 V s�1,

(c) Chronoamperometry curves at 0.6 V in a 1.0 M

CH3OH + 0.5 M H2SO4 solution.

C A R B O N 5 0 ( 2 0 1 2 ) 3 0 3 2 – 3 0 3 8 3037

not only a higher initial current but also a higher current at

the same time compared to the others. This indicated that

the Pt/ND/G-1200 catalyst displayed better catalytic activity

and stability. Although the GND-1500 supported Pt exhibited

a high initial current, the rapid decrease in current showed

its poorer stability than Pt/GND-1200.

4. Conclusions

A core/shell structural ND/G was produced by annealing ND

in a 10�3 Pa vacuum at 1200 and 1500 �C. Few-layer graphene

formed on the ND surface and the layer number increased

with increased annealing temperature. ND/G- and ND-sup-

ported Pt electrocatalysts were prepared using the microwave

heating method. Pt nanoparticles with 3–5 nm in diameter

were obtained and a higher dispersion was observed on the

ND/G support. The electrochemical results showed that the

Pt/ND/G catalyst had better catalytic activity and greater sta-

bility for methanol electro-oxidation in comparison to Pt/ND

prepared under the same conditions. ND/G with high conduc-

tivity and high electrochemical stability is a good candidate

for a catalyst support in electrochemical applications.

Acknowledgements

This work was supported by the National Natural Science

Foundation of China (Nos. 50872119 and 50972125), the Natu-

ral Science Foundation of Hebei Province (Nos. E2012203112

and E2011203126), and the China Postdoctoral Science Foun-

dation (20100480197). The authors gratefully acknowledge

the financial and material support from Element Six Co.

R E F E R E N C E S

[1] Geim AK. Graphene: status and prospects. Science2009;324(5934):1530–4.

[2] Soldano C, Mahmood A, Dujardin E. Production, propertiesand potential of graphene. Carbon 2010;48(8):2127–50.

[3] Li X, Wang X, Zhang L, Lee S, Dai H. Chemically derived,ultrasmooth graphene nanoribbon semiconductors. Science2008;319(5867):1229–32.

[4] Stankovich S, Dikin DA, Dommett GHB, Kohlhaas KM, ZimneyEJ, Stach EA, et al. Graphene-based composite materials.Nature 2006;442(7100):282–6.

[5] Schedin F, Geim A, Morozov S, Hill E, Blake P, Katsnelson M,et al. Detection of individual gas molecules adsorbed ongraphene. Nat Mater 2007;6(9):652–5.

[6] Yoo EJ, Kim J, Hosono E, Zhou H, Kudo T, Honma I. Largereversible Li storage of graphene nanosheet families for usein rechargeable lithium ion batteries. Nano Lett2008;8(8):2277–82.

[7] Chen Y, Zhang X, Zhang D, Yu P, Ma Y. High performancesupercapacitors based on reduced graphene oxide in aqueousand ionic liquid electrolytes. Carbon 2011;49(2):573–80.

[8] Dong L, Gari RRS, Li Z, Craig MM, Hou S. Graphene-supportedplatinum and platinum–ruthenium nanoparticles with highelectrocatalytic activity for methanol and ethanol oxidation.Carbon 2010;48(3):781–7.

[9] Xin Y, Liu J, Liu W, Gao J, Xie Y, Yin Y, et al. Preparation andcharacterization of Pt supported on graphene with enhancedelectrocatalytic activity in fuel cell. J Power Sources2010;196:1012–8.

[10] Li Y, Tang L, Li J. Preparation and electrochemicalperformance for methanol oxidation of Pt/graphenenanocomposites. Electrochem Commun 2009;11(4):846–9.

[11] Zhang L, Li X, Huang Y, Ma Y, Wan X, Chen Y. Controlledsynthesis of few-layered graphene sheets on a large scaleusing chemical exfoliation. Carbon 2010;48(8):2367–71.

[12] Tung VC, Allen MJ, Yang Y, Kaner RB. High-throughputsolution processing of large-scale graphene. Nat nanotechnol2008;4(1):25–9.

[13] Shin HJ, Kim KK, Benayad A, Yoon SM, Park HK, Jung IS, et al.Efficient reduction of graphite oxide by sodium borohydride

3038 C A R B O N 5 0 ( 2 0 1 2 ) 3 0 3 2 – 3 0 3 8

and its effect on electrical conductance. Adv Funct Mater2009;19(12):1987–92.

[14] Yan J, Wei T, Shao B, Ma F, Fan Z, Zhang M, et al.Electrochemical properties of graphene nanosheet/carbonblack composites as electrodes for supercapacitors. Carbon2010;48(6):1731–7.

[15] Yu D, Dai L. Self-assembled graphene/carbon nanotubehybrid films for supercapacitors. J Phys Chem Lett2009;1(2):467–70.

[16] Biswas S, Drzal LT. Multilayered nano-architecture of variablesized graphene nanosheets for enhanced supercapacitorelectrode performance. ACS Appl Mater Interface2010;2:2293–300.

[17] Zang JB, Wang YH, Zhao SZ, Bian LY, Lu J. Electrochemicalproperties of nanodiamond powder electrodes. Diam RelatMater 2007;16(1):16–20.

[18] Holt KB, Ziegler C, Caruana DJ, Zang J, Millan-Barrios EJ, Hu J,et al. Redox properties of undoped 5 nm diamondnanoparticles. Phys Chem Chem Phys 2008;10(2):303–10.

[19] Zhao W, Xu JJ, Qiu QQ, Chen HY. Nanocrystalline diamondmodified gold electrode for glucose biosensing. BiosensBioelectron 2006;22(5):649–55.

[20] Bian L, Wang Y, Zang J, Yu J, Huang H. Electrodeposition of Ptnanoparticles on undoped nanodiamond powder formethanol oxidation electrocatalysts. J Electroanal Chem2010;644(1):85–8.

[21] Bogatyreva G, Marinich M, Ishchenko E, Gvyazdovskaya V,Bazalii G, Oleinik N. Application of modified nanodiamondsas catalysts of heterogeneous and electrochemical catalyses.Phys Sol State 2004;46(4):738–41.

[22] Shao Y, Liu J, Wang Y, Lin Y. Novel catalyst support materialsfor PEM fuel cells: current status and future prospects. JMater Chem 2008;19(1):46–59.

[23] Prawer S, Nugent K, Jamieson D, Orwa J, Bursill LA, Peng J.The Raman spectrum of nanocrystalline diamond. ChemPhys Lett 2000;332(1–2):93–7.

[24] Allen MJ, Tung VC, Kaner RB. Honeycomb carbon: a review ofgraphene. Chem Rev 2009;110(1):132–45.

[25] Lee J-M, Han S-B, Kim J-Y, Lee Y-W, Ko AR, Roh B, et al.TiO2@carbon core–shell nanostructure supports for platinumand their use for methanol electrooxidation. Carbon2010;48(8):2290–6.

[26] Qi J, Yan S, Jiang Q, Liu Y, Sun G. Improving the activity andstability of a Pt/C electrocatalyst for direct methanol fuelcells. Carbon 2010;48(1):163–9.

[27] Zhao J, Wang P, Chen W, Liu R, Li X, Nie Q. Microwavesynthesis and characterization of acetate-stabilized Ptnanoparticles supported on carbon for methanol electro-oxidation. J Power Sources 2006;160(1):563–9.

[28] Chen WX, Lee JY, Liu Z. Microwave-assisted synthesis ofcarbon supported Pt nanoparticles for fuel cell applications.Chem Commun 2002;21:2588–9.

[29] Li X, Chen W, Zhao J, Xing W, Xu Z. Microwave polyolsynthesis of Pt/CNTs catalysts: effects of pH on particle sizeand electrocatalytic activity for methanol electrooxidization.Carbon 2005;43(10):2168–74.

[30] Sharma S, Ganguly A, Papakonstantinou P, Miao X, Li M,Hutchison JL, et al. Rapid microwave synthesis of CO tolerantreduced graphene oxide-supported platinum electrocatalystsfor oxidation of methanol. J Phys Chem C 2010;114:19459–66.

[31] Zhou M, Zhang A, Dai Z, Zhang C, Feng YP. Greatly enhancedadsorption and catalytic activity of Au and Pt clusters ondefective graphene. J Chem Phys 2010;132:194704–6.

[32] Yoo EJ, Okata T, Akita T, Kohyama M, Nakamura J, Honma I.Enhanced electrocatalytic activity of Pt subnanoclusters ongraphene nanosheet surface. Nano Lett 2009;9(6):2255–9.

[33] Kongkanand A, Kuwabata S, Girishkumar G, Kamat P. Single-wall carbon nanotubes supported platinum nanoparticleswith improved electrocatalytic activity for oxygen reductionreaction. Langmuir 2006;22(5):2392–6.

[34] Tong X, Zhao G, Liu M, Cao T, Liu L, Li P. Fabrication and highelectrocatalytic activity of three-dimensional porousnanosheet Pt/boron-doped diamond hybrid film. J Phys ChemC 2009;113(31):13787–92.