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Materials Science and Engineering B 176 (2011) 785–791

Contents lists available at ScienceDirect

Materials Science and Engineering B

journa l homepage: www.e lsev ier .com/ locate /mseb

lectrochemical co-deposition of bimetallic Pt–Ru nanoclusters dispersed onoly(3,4-ethylenedioxythiophene) and electrocatalytic behavior forethanol oxidation

. Patraa, Sthitaprajna Dasha, V. Anandb, C.S. Nimishab, G.M. Raob, N. Munichandraiaha,∗

Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, IndiaDepartment of Instrumentation, Indian Institute of Science, Bangalore 560 012, India

r t i c l e i n f o

rticle history:eceived 25 May 2010eceived in revised form 16 February 2011ccepted 20 March 2011

a b s t r a c t

Nanoclusters of bimetallic Pt–Ru are electrochemically deposited on conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), which is also electrochemically deposited on a carbon paper substrate.The bimetallic deposition is carried out in an acidic electrolyte consisting of chloroplatinic acid and ruthe-nium chloride at 0.0 V versus saturated calomel electrode (SCE) on PEDOT coated carbon paper. A thinlayer PEDOT on a carbon paper substrate facilitates the formation of uniform, well-dispersed, nano clus-

eywords:t–Ru nanoclusterslectrodeposition-ray photoelectron spectroscopyethanol electrooxidation

yclic voltammetrymperometry

ters of Pt–Ru of mean diameter of 123 nm, which consist of nanosize particles. In the absence of PEDOT,the size of the clusters is about 251 nm, which are unevenly distributed on carbon paper substrate.Cyclic voltammetry studies suggest that peak currents of methanol oxidation are several times greateron PtRu–PEDOT electrode than on Pt–Ru electrode in the absence of PEDOT.

© 2011 Elsevier B.V. All rights reserved.

. Introduction

Among various catalyst materials studied for electrooxidationf methanol, bimetallic Pt–Ru exhibits tolerance towards poison-ng and sustains electrocatalytic activity for studies related toirect methanol fuel cells [1–9]. A thin film of an electronicallyonducting polymer (CP) acts as a good dispersion medium foratalyst particles and also it improves the interfacial propertiesetween the electrode and the electrolyte. Polymer films, such asolypyrrole (PPY), polyaniline (PANI), poly(3-methylethiophene)PMT), poly(3,4-ethylenedioxythiophene) (PEDOT) etc., have beennvestigated as CPs for supporting catalyst particles for methanolxidation [10–19]. These studies include Pt modified PANI [10–12],t nanoparticle-supported PPY nanotubes [13], Pt particles dis-ersed on PANI/carbon nanotubes (CNT) composites [14], Pt andt–Ru nanoparticle modified PPY/CNT composites [15] and Pt mod-fied poly(3-methyl thiophene) [16]. PEDOT was employed as aispersion medium for Pt particles in only a few studies [17–19].uo et al. [17] prepared PEDOT–poly(styrene sulfonic acid) (PSS)

oated indium tin oxide (ITO) electrode and Pt particles wereeposited by cyclic voltammetry in a H2PtCl6 solution. The catalyticctivity of Pt–PEDOT–PSS/ITO electrode for methanol oxidation was

∗ Corresponding author. Tel.: +91 80 22933183; fax: +91 80 23600683.E-mail address: muni@ipc.iisc.ernet.in (N. Munichandraiah).

921-5107/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.mseb.2011.03.012

studied. In another study, Drillet et al. [18] polymerized a monomersolution to PEDOT powder by chemical oxidation using Na2S2O8as the oxidizing agent. Pt particles were deposited on to PEDOTpowder by reducing H2PtCl2 using formaldehyde and methanoloxidation was studied. We have recently reported electrodeposi-tion of nanoclusters of Pt on electrochemically polymerized PEDOTon carbon paper electrodes and studied methanol oxidation [19].In a recent study, Tintula et al. [20] compared catalytic activity ofPtRu particles dispersed on PEDOT and carbon powder towardsmethanol oxidation. Both PEDOT and PtRu were prepared by chem-ical routes and it was observed that the catalytic activity of PtRupresent on PEDOT was superior to the same catalyst present oncarbon powder. For the purpose of reducing methanol crossoverin a direct methanol fuel cell, Stanis et al. [21] coated the anodegas diffusion layer with PEDOT and found that methanol per-meability was reduced. Arbizzania et al. [22] studied methanoloxidation on Pt and PtRu catalyst prepared by chemical and elec-trochemical routes on PEDOT, which was prepared by a chemicalroute.

It is understood from the above literature that the catalyst par-ticles dispersed on a conducting polymer exhibit greater catalyticactivity than the same materials in the absence of the conduct-

ing polymer. To the best of authors’ knowledge there are noreports on electrodeposition of bimetallic Pt–Ru in nano dimen-sions on electrochemically prepared conducting polymer PEDOT.In the present study, nanoclusters of Pt–Ru are electrochemically

7 and Engineering B 176 (2011) 785–791

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Fig. 1. (A) Cyclic voltammogram of carbon paper in 0.1 M H2SO4 + 0.01 MEDOT + 0.01 M SDS at 10 mV s−1 between 0 and 1.20 V. (B) (i) Cyclic voltammogram

86 S. Patra et al. / Materials Science

eposited in a single step on electrochemically prepared PEDOT.he presence of PEDOT facilitates uniform distribution of Pt–Ruanoclusters. Studies of electrochemical oxidation of methanoluggest a beneficial effect of PEDOT on electrocatalysis by Pt–Ruanoclusters.

. Experimental

3,4-Ethylenedioxythiophene (EDOT) monomer was purchasedrom Aldrich and analytical grade H2SO4 from Merck. Reagentrade sodium dodecylsulfate (SDS, C12H25NaOSO3) from Merckas used as the surface-active agent for preparation of PEDOT.2PtCl6, 6H2O and RuCl3, H2O were purchased from Kemie Lab.Toray carbon paper foil (thickness: 0.2 mm) was used as the

ubstrate for electrodeposition of PEDOT. All solutions were pre-ared in doubly distilled water. A glass cell of about 50 ml capacityith suitable ground-glass joints to introduce a working elec-

rode, Pt foil auxiliary electrodes, and a saturated calomel referencelectrode (SCE) was used for electrochemical deposition and char-cterization studies. All potential values are reported againstCE.

A foil of 0.7 cm in width and 3.0 cm in length was sectioned outf a carbon paper, 1.4 cm2 area at one of the ends was exposedo the electrolyte and the rest of its length was used to takelectrical contact through a Cu wire. The unexposed area wasasked with a PTFE tape to ensure that the electrolyte contacts

nly the required area. An electrolyte of 0.1 M H2SO4 + 0.01 MDOT + 0.01 M SDS was used for PEDOT deposition. The elec-rodeposition was carried out at a constant potential of 0.9 V,s reported previously and the corresponding charge was mea-ured [23,24]. The quantity of PEDOT deposited on the substratencreased with an increase in charge passed. Thus, the charge

as used as a measure to estimate the mass of PEDOT. For theresent experiments, PEDOT was prepared with 0.07 C cm−2. Afterhe electrochemical deposition of PEDOT, the electrode was sep-rated from the cell, washed repeatedly in 0.1 M H2SO4 solutionnder stirring for about 30 min. Pt–Ru particles were potentio-tatically deposited at 0.0 V in an aqueous electrolyte consistingf 0.1 M H2SO4 + 0.002 M H2PtCl6 + 0.002 M RuCl3. A few Pt–PEDOTnd Ru–PEDOT electrodes were also prepared by depositing Pt in.1 M H2SO4 + 0.002 M H2PtCl6 and Ru in 0.1 M H2SO4 + 0.002 MuCl3 electrolytes at 0.0 V. Ru–PEDOT electrode, however, did notxhibit electrochemical activity similar to the results reported onu without PEDOT [25–27]. Electrodes were also made by deposit-

ng metal nanoclusters on bare carbon paper (without PEDOT)or studies of comparison. Several preliminary experiments wereonducted to arrive at 0.0 V as the potential suitable for depo-ition Pt–Ru nanoparticles. The presence of Pt and Ru in theimetallic coatings was observed by analysis of X-ray photoelec-ron spectra (XPS). It was attempted to measure the real surfacerea of PtRu deposits by CO adsorption followed by anodic oxi-ation. For a PtRu–PEDOT coated carbon paper electrode (300 �gf catalyst), the surface area calculated was 25 m2 g−1. However,eometric area of carbon paper substrate was used for calculationf current density as this study involves comparison to under-tand the effect of PEDOT. Masses of electrodeposited Pt and PtRuere calculated from the charge passed during deposition. As the

oncentrations of H2PtCl6 and RuCl3 were 0.002 M, the chargeas assumed to be equally shared for the reduction of Pt4+ andu3+.

Potentiostatic deposition of PEDOT, Pt, Ru and Pt–Ru as well as

yclic voltammetry experiments were carried out using an EG&GARC potentiostat/galvanostat model Versastat or a Solartronlectrochemical interface model SI 1287. Electron microscopicmages were recorded using FEI Company scanning electron micro-

of carbon paper in 0.1 M H2SO4 + 0.01 M EDOT + 0.01 M SDS at 10 mV s−1 between0 and 1.50 V, and (ii) cyclic voltammogram of PEDOT coated carbon paper in 0.1 MH2SO4 at 10 mV s−1 between 0 and 1.0 V.

scope (SEM) model Sirion and transmission electron microscope(HRTEM) model TECNAI F30. X-ray diffraction (XRD) patterns wererecorded using Philips diffractometer model X’PERT PRO usingCuK� (� = 1.5418 A) as the source. XPS spectra were recordedusing SPECS photoelectron spectrometer with Mg as the source.While samples consisting of carbon paper coated electrodeswere used for recording XRD, SEM and XPS data, electrodeswere sonicated in acetone to disperse the coated materials forTEM studies. Acetone consisting of the dispersed material wasadded onto carbon coated Cu grids for recording TEM images.All experiments were conducted in an air-conditioned room at22 ± 1 ◦C.

3. Results and discussion

3.1. Preparation of PEDOT, Pt, Ru and Pt–Ru

Electrochemical oxidation of EDOT monomer in an acidic elec-trolyte produces PEDOT in the form of a coating on the anode. Ithas been shown that adherence between the substrate and thePEDOT improves when SDS is present in the electrolyte as the

surfactant [23]. Cyclic voltammogram of carbon paper in EDOTcontaining electrolyte is shown in Fig. 1A. Current starts increas-ing at 0.8 V due to oxidation of EDOT to PEDOT. However, if thecyclic voltammogram is recorded between 0 and 1.50 V (Fig. 1B,

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peaks at 2� = 42.6, 54.5, 77.4 and 86.7 are attributed to carbonpaper used in the present work. The XRD pattern of Ru–PEDOT(curve (iii)) shows no peaks related to crystalline Ru, thus, indi-cating that the electrodeposited Ru is amorphous. Furthermore,

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ig. 2. (A) SEM micrograph of PEDOT coated carbon paper, and (B) IR spectra ofEDOT and PtRu–PEDOT samples.

urve (i)), two current peaks are observed. The peak appearing at.90 V is attributed to oxidation of EDOT to PEDOT, and the peakt 1.40 V is due to oxidation of PEDOT. Hence 0.90 V was chosenor the deposition of PEDOT in the present work. After depositionf PEDOT, the electrode was washed in dil. H2SO4 solution andyclic voltammograms were recorded in dil. H2SO4 solution (Fig. 1B,urve (ii)). The current is low and there are no current peaks.hese results confirm that the formation of PEDOT at 0.90 V occursithout PEDOT itself undergoing further oxidation, and PEDOT is

table in the potential range between 0 and 1.0 V. The mass ofEDOT was calculated from charge using Faraday’s law. The valuef charge 0.07 C cm−2 generally used for preparation correspondso 53 �g cm−2 of PEDOT. The PEDOT coated carbon paper elec-rodes were subjected to SEM and IR spectroscopy studies (Fig. 2).orous morphology of PEDOT is observed. The IR spectrum is inood agreement with previously reported study [28]. The IR bandt 1338 cm−1 is due to C–C or C C stretching of thiophene ring. Theand at 1516 cm−1 is attributed to ring stretching. The peaks cor-esponding to C–S bond stretching in thiophene ring are observedt 1186, 1140 and 1085 cm−1 [28]. These observations suggest thathe carbon paper substrate is coated with PEDOT. A cyclic voltam-

ogram of a PEDOT coated carbon paper in 0.1 M H2SO4 + 0.002 M2PtCl6 + 0.002 M RuCl3 electrolyte is shown in Fig. 3. Current peaks

orresponding to the reduction of Pt4+ and Ru3+ appear at 0.32 and.19 V, respectively. For potentiostatic deposition of PtRu, 0.0 V washosen and the deposition was continued till the required chargeas passed. IR spectrum recorded for PtRu–PEDOT was similar to

Fig. 3. Cyclic voltammogram of PEDOT coated carbon paper in 0.1 MH2SO4 + 0.002 M H2PtCl6 + 0.002 M RuCl3 at 10 mV s−1.

that of PEDOT (Fig. 2B), suggesting absence of chemical interactionbetween PEDOT and PtRu bimetallic particles.

3.2. XRD studies

XRD patterns of bare carbon paper, and carbon papers coatedwith PEDOT, Pt–PEDOT, Ru–PEDOT and PtRu–PEDOT electrodeswere recorded (Fig. 4). The XRD pattern of Pt–PEDOT (curve(iv)) is indexed to fcc unit cell of Pt (JCPDS File No. 7440-06-4). The peaks at 2� = 39.9, 46.3, 67.8 and 81.3◦ are assigned to(1 1 1), (2 0 0), (2 2 0) and (3 1 1) planes, respectively. The peaksobserved at 2� = 42.6, 54.5, 77.4 and 86.7◦ are also presentin the XRD patterns of carbon (curve (i)) as well as PEDOTcoated carbon paper (curve (ii)) electrodes. The patterns of car-bon paper (curve (i)) and PEDOT coated carbon paper (curve(ii)) are identical suggesting amorphous nature of PEDOT. The

◦

2 θ / degree

Fig. 4. X-ray diffraction patterns of (i) carbon paper, (ii) PEDOT coated carbon paper,(iii) Ru–PEDOT coated carbon paper, (iv) Pt–PEDOT coated carbon paper and (v)PtRu–PEDOT coated carbon paper electrodes.

788 S. Patra et al. / Materials Science and Engineering B 176 (2011) 785–791

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ig. 5. SEM images of (A and C) PtRu coated carbon paper, and (B and D) PtRu–PEDE) PtRu and (F) PtRu–PEDOT are shown here.

he XRD patterns (curve (v)) of PtRu–PEDOT prepared in 0.002 M2PtCl6 + 0.002 M RuCl3 electrolyte are similar to the pattern oft–PEDOT. Thus, Ru remains amorphous in bimetallic state also.tRu–PEDOT electrodes prepared in solutions of higher RuCl3oncentration also exhibited similar XRD patterns. The presencef amorphous Ru agrees with reported literature [29,30]. Broadiffraction peaks of Pt–PEDOT and PtRu–PEDOT indicate small crys-al size.

.3. Microscopy

SEM images of PtRu–PEDOT coated carbon paper electrode pre-

ared in 0.002 M H2PtCl6 + 0.002 M RuCl3 solution are shown inifferent magnifications (Fig. 5B and D). Agglomerated particles areniformly distributed on the electrode surface. The average sizef agglomerates is 123 nm obtained from the fitting of histograms

ted carbon paper electrodes with metal loading level of 30 �g cm−2. Histograms of

(Fig. 5F). However, in SEM images of Pt–Ru coated carbon paperelectrode (in the absence of PEDOT) bigger clusters (average sizeof the particles is 251 nm (Fig. 5E)) which are unevenly distributedon the surface of bare carbon paper are noticed (Fig. 5A and C). Thethin film of PEDOT possesses surface defects uniformly distributedon its surface, and each defect acts as a nucleation center for theformation of metal atoms. Growth of these metal atoms occurson continuing the electrolysis, which results in the formation ofuniformly distributed nanosize clusters (Fig. 5B and D). The Pt–Ruaggregates on PEDOT are composed of small particles, which is evi-dent from TEM images. TEM image (Fig. 6A) shows that the particlesize is in the range of 4–6 nm. The HRTEM micrograph (Fig. 6B)

provides lattice fringes with a separation of 1.21 and 2.19 A. Thesevalues correspond to (3 1 1) and (1 1 1) planes, respectively, of fcclattice of Pt. The EDAX data (Fig. 6C) confirm the presence of Pt andRu.

S. Patra et al. / Materials Science and Engineering B 176 (2011) 785–791 789

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Fig. 6. (A) TEM image, (B) HRTEM ima

It is known that electrochemically deposited Pt based metalanoparticles tend to agglomerate instead of dispersing as indi-idual isolated nanoparticles on the surface of the substrate.aillard et al. [31] electrochemically deposited Pt in 0.007 M2PtCl6 + 0.01 M HCl on a glassy carbon electrode by a potential

weep technique. TEM images show the presence of agglomer-ted nanograined Pt structures, but not isolated nanoparticles. Theggregates ranged in size from 25 to 100 nm, which consisted oft nanoparticles of 6–7 nm in diameter. The formation of Pt aggre-ates was attributed to 3D nucleation and growth mechanism. Apontaneous deposition of Pt on Ru surface revealed a 3D globulargglomerated nanocluster which was evident from scanning tun-eling microscopy study [32]. An average diameter of 25–30 nmas reported for the nanoclusters. Similar to these studies [31,32],

he electrochemically deposited Pt–Ru in the present study consistf nanoclusters.

.4. X-ray photoelectron spectroscopy

PtRu–PEDOT/C electrodes were investigated by recording XPSpectra. Fig. 7A shows the Pt 4f region of the XPS spectrum oftRu–PEDOT/C, which could be deconvoluted into two pairs of dou-

lets. For each doublet, the binding energy (BE) of Pt 4f5/2 is higherhan that of Pt 4f7/2 by 3.3 eV [33]. The most intense doublet appear-ng at 71.5 and 74.8 eV is the signature of metallic Pt. The bindingnergy 71.5 eV for Pt 4f7/2 is close to 71.2 eV reported for 4f7/2

d (C) EDAX spectrum of PtRu–PEDOT.

of bulk Pt [34,35]. The weaker doublet at higher BEs at 74.8 and78.1 eV, is attributed to a small amount of Pt4+ residue on the sur-face [36]. Fig. 7(B–D) shows the XPS data for Ru 3p, S 2p and O1s regions, respectively. Ru 3p peak could be deconvoluted intotwo peaks. The broad peak (Fig. 7B) at 462.6 eV indicates the pres-ence of Ru0 and peak at 467.8 eV indicates Ru2+ states, respectively[37]. The S 2p core-level high resolution XPS spectrum (Fig. 7C)corresponds to single sulfur bonding environment in PEDOT with aspin-split doublet, S 2p1/2 and S 2p3/2 [38–40]. The asymmetric tailto higher binding energy is related to the doping process, in whichthe delocalized �-electrons in thiophene ring broaden the bindingenergy of the S atom. In O1s core-level XPS spectrum (Fig. 7D), apeak at 533.2 eV corresponds to the sole oxygen binding environ-ment in PEDOT and peak at 532.0 eV is due to loosely bound surfaceoxygen [39].

3.5. Electrooxidation of methanol

Fig. 8A shows cyclic voltammograms of Pt–PEDOT (curve i) andPtRu–PEDOT (curve ii) electrodes in 0.1 M H2SO4 + 1.0 M CH3OHsolution, at a sweep rate of 5 mV s−1 recorded in the first cycle.Charges used for deposition of metal particles in Pt and Pt–Ru

electrodes are 0.057 and 0.114 C cm−2, respectively. Pt–PEDOT/Celectrode exhibits two oxidation peaks, P1 and P2 (Fig. 8, curve ii),which correspond to the oxidation of methanol during the forwardand reverse sweeps at 0.61 and 0.46 V, respectively. The shape of

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he curves and the range of peak potentials are in accordance withrevious work [7,8]. In the case of PtRu–PEDOT electrode (Fig. 8,urve ii), these peaks appear at potentials, 0.46 and 0.36 V, respec-ively. The onset potential of methanol oxidation on Pt–PEDOTlectrode is about 0.30 V, whereas it is about 0.15 V on PtRu–PEDOTlectrode. The mechanism of electrooxidation of methanoln Pt–Ru bimetallic catalyst includes the following importanttages [41].

t–Ru + CH3OH → (Pt–CO)–Ru + 4H+ + 4e− (1)

Pt–CO)–Ru + H2O → (Pt–CO)–(Ru-OH) + H+ + e− (2)

Pt–CO)–(Ru-OH) → Pt–Ru + CO2 + H+ + e− (3)

eaction (1) occurs in four different steps, and each step involvesingle electron transfer process [41]. Thus several intermediatepecies of the type CHxO (0 < x < 4) are expected to be formed.dsorption of CO intermediate occurs on Pt sites (Reaction (1)). Oxi-ation of H2O (Reaction (2)) leading to the formation of adsorbedH takes place on Ru sites. Adsorbed CO and OH on adjacent sitesf Pt and Ru, respectively, combine resulting in the formation of thenal product, CO2 (Reaction (3)). While the formation of adsorbedH takes place on Ru sites in the case of Pt–Ru bimetallic cata-

yst, this process as well as the formation of adsorbed CO occurn Pt sites only in the case of Pt catalyst. Pt–Ru, thus, is a bet-er catalyst for methanol oxidation. The lower onset potential asell as lower peak potentials on PtRu–PEDOT electrode than on

t–PEDOT electrode support greater catalytic activity of the formerlectrode.

To study the effect of PEDOT, Pt–Ru catalyst was deposited onare carbon paper and voltammograms were recorded in 0.1 M

2SO4 + 1.0 M CH3OH solution at 5 mV s−1 (Fig. 8B). The shape of

he voltammogram and also the peak potentials were the sames those of curve (ii) in Fig. 8A. However, the current values aremaller by about 7.5 times for the electrode in the absence of PEDOT.

1s regions of PtRu–PEDOT coated carbon electrode.

This is due to the fact that the bimetallic catalyst particles tend togrow into non-uniformly distributed, large agglomerates on barecarbon paper (Fig. 4C and D). Thus, a thin layer of PEDOT as a sup-port for uniform distribution of electrodeposited Pt–Ru (Fig. 5A andB), favours a high catalytic efficiency. The mass specific current(mA mg−1) is calculated from the forward peak current (mA) andmass of the catalyst (mg). A value of 657 mA mg−1 is obtained forthe PtRu–PEDOT electrode prepared in 0.002 M H2PtCl6 + 0.002 MRuCl3 electrolyte. The corresponding value for PtRu electrode (inthe absence of PEDOT) is 98 mA mg−1.

The ratio of forward peak current (If) to backward peak cur-rent (Ib) is considered as a measure of the efficiency of catalysts.Raghuveer and Manthiram reported the value of If/Ib ratio ofcommercial ETEK catalyst as unity [42]. Pt and Pt–Ru decoratedpolypyrrole/multiwalled carbon nanotubes show maximum If/Ibratio as 1.2 [15]. Heat treated Pt and Pt52Ru48 supported by carbonshowed the If/Ib ratio are 0.87 and 2.30 respectively [43]. Potentio-dynamically or pulse galvanostatically deposited Pt on polyanilinemicro-fiber shows the value of If/Ib ratio as 1.7 [44]. In the presentstudy, If/Ib ratio calculated for several repetitive voltammogramsfor Pt–PEDOT and PtRu–PEDOT electrodes. For Pt–PEDOT elec-trodes, the If/Ib ratio is about 1.5 for all cycles tested. However,this ratio is greater than 3.0 for PtRu–PEDOT/C electrodes, suggest-ing a higher catalytic efficiency of the catalyst in the presence ofPEDOT.

The stability of PtRu–PEDOT electrodes was studied by repeatedcycling of the electrode in 0.1 M H2SO4 consisting of 1 M CH3OH.There was a gradual decrease of cyclic voltammetric peak currentsin about 10 cycles and thereafter reproducible stable voltam-mograms were recorded. The decrease in magnitude of peak

currents after the initial ten cycles was about 5% in relation tothe first voltammogram. Amperometry data recorded at five differ-ent potentials in a stirred solution consisting of 0.1 M H2SO4 + 1 MCH3OH are shown in Fig. 9. The measured current is fairly stable for

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Fig. 8. (A) Cyclic voltammograms of (i) Pt–PEDOT (mass of Pt: 14 �g cm−2) and (ii)PtRu–PEDOT (mass of Pt: 13 �g cm−2) electrodes in 1 M CH3OH + 0.1 M H2SO4 at asweep rate of 5 mV s−1. (B) Cyclic voltammograms of PtRu (mass of Pt: 13 �g cm−2)in the absence of PEDOT in 1 M CH3OH + 0.1 M H2SO4 at a sweep rate of 5 mV s−1.

Fig. 9. Current–time plots of PtRu–PEDOT (mass of Pt: 13 �g cm−2) electrode at (i)0.70, (ii) 0.75 (iii) 0.80, (iv) 0.85 and (v) 0.90 V vs. SCE.

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about 1 h tested. Current oscillations are reflected in appearance ofthe curves as thick bands.

4. Conclusions

Nanoclusters of bimetallic Pt–Ru electrodeposited on PEDOTexhibit a high catalytic activity for methanol oxidation. A thin layerPEDOT on a carbon paper substrate facilitates the formation ofuniform, well-dispersed, nano clusters of Pt–Ru of mean diame-ter of 123 nm, which consist of nanosize particles. In the absence ofPEDOT, the size of the clusters is about 251 nm, which are unevenlydistributed on carbon paper substrate. The cyclic voltammetrystudies suggest that peak currents of methanol oxidation are sev-eral times greater for PtRu–PEDOT electrode than Pt–Ru electrode.Results presented in the paper reflect the importance of conductingpolymer, PEDOT for uniform distribution of the catalyst particles.For the first time in the literature, PEDOT as well as Pt–Ru nanoclus-ters are electrochemically deposited and electrocatalytic activitytowards methanol oxidation is studied.

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