Electroactivity of Pt-Ru-polyaniline composite catalyst-electrodes prepared by electrochemical depos(8)

Inthecaseofthepolyaniline-supportedcatalysts,thecyclicvoltammogramsshowninFig.7alsoexhibitmethanoloxi-dationpeak.ThecatalystdepositedonPANIshowedaratherdefiniteoxidationpeakat~520mV.SimilartotheCBssup-ports,thecatalystsshowedthehighestelectroactivityat24min

Fig.6.CyclicvoltammogramsofPt–Ru/CBscatalystspreparedfordifferentplatingtimesof(a)6,(b)12,(c)24,and(d)36minin1Mmethanolsolution(scanrate:20

mV/s).

Fig.7.CyclicvoltammogramsofPt–Ru/polyanilinecatalystspreparedfordifferentplatingtimesof(a)6,(b)12,(c)24,and(d)36minin1Mmethanolsolution(scanrate:20

mV/s).

plating.Indeed,thecatalystsby24minplatingexhibitedanaveragesizeof3.1nm,whereasthecatalystsby36minplatingshowedanaveragesizeof4.2nm.Smallerparticlesofcatalystsmightresultinalargeavailablecatalystsurfaceareaandgoodelectrocatalyticpropertiesformethanoloxidation.

TodeterminethecarbonandPANIsupportinfluences,in-dividually,ontheoxidationcurrentofcatalysts,supportswith-outmetalcatalystswerestudiedin1MCH3OH+0.5MH2SO4aqueoussolution,asshowninFig.8.Thecarbonsupportdidnotshowanyelectrochemicalactivityexceptforsomesmallcapacitivecurrent.Bycontrast,thePANIsupportshowedadefinitecathodic/anodicpeak,indicatinganoxidation/reductionreaction[38–40].However,itwasconcludedthatpolyanilinesupportscouldnotfunctionaloneascatalystsformethanoloxidation.

Tocheckthespecificsurfaceareaofcatalysts,cyclicvol-tammograms(CVs)hadbeenperformed.Fig.9showstheCVsofthePANI-orCBs-supportedcatalystsin1.0Msulphuricacidsolution.H2adsorption/desorptionpeakwereobservedat 200mVforbothcaseandtheelectrochemicalsurfaceareaarecalculated(PtRu/PANI:4.3cm2,PtRu/CBs:7.4cm2).

By

Fig.8.Cyclicvoltammogramsof(a)CBsand(b)polyanilinesupportsin1Mmethanolsolution(scanrate:20mV/s).

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