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Article (Special Column on Electrocatalysis for Fuel Cells) 

Core‐shellgraphene@amorphouscarboncompositessupportedplatinumcatalystsforoxygenreductionreaction

HuiWu,TaoPeng,ZongkuiKou,JianZhang,KunCheng,DapingHe,MuPan,ShichunMu*

StateKeyLaboratoryofAdvancedTechnologyforMaterialsSynthesisandProcessing,WuhanUniversityofTechnology,Wuhan430070,Hubei,China

A R T I C L E I N F O  

A B S T R A C T

Articlehistory:Received12July2014Accepted22August2014Published20April2015

  A core‐shell graphene nanosheets (GNS) and amorphous carbon composite (GNS@a‐C)was pre‐paredbyachlorinationmethodandusedasahighlyefficientcatalystsupportforoxygenreductionreaction.Herein,GNS as a shell,with excellent conductivity, high surface area, and corrosion re‐sistance, served as a protecting coating to alleviate the degradation of amorphous carbon core.Platinumnanoparticleswerehomogeneouslydepositedonthecarbonsupport(Pt/GNS@a‐C)andshowed a good catalytic activity and a higher electrochemical stability when compared with acommercialPt/Ccatalyst.ThemassactivityofPt/GNS@a‐Ccatalystwas0.121A/mg,whichwasalmosttwiceashighasthatofPt/C(0.064A/mg).Moreover,Pt/GNS@a‐Cretained51%ofitsinitialelectrochemicalspecificareaafter4000operatingcycleswhencomparedwithPt/C(33%).Thus,thepreparedcatalystfeaturedexcellentelectrochemicalstability,showingpromiseforapplicationinpolymerelectrolytemembranefuelcells.

©2015,DalianInstituteofChemicalPhysics,ChineseAcademyofSciences.PublishedbyElsevierB.V.Allrightsreserved.

Keywords:Low‐temperaturefuelcellSupportCore‐shellstructureOxygenreductionreaction

 

 

1. Introduction

Polymer electrolyte membrane fuel cells (PEMFCs) havebeen considered as an environmentally friendly solution forautomotive, backup, and residential power needs. However,PEMFCsareyettobeimplementedonacommercialscale.Oneof the most important factors preventing their commercialimplementation is the severe degradation of the traditionalPt/C catalyst employed in PEMFCs. For example, amorphouscarbon, which is a commonly used carbon support, is susc‐eptible to corrosive conditions [1] including highwater cont‐ent, low pH (< 1), relatively high temperatures (~50–90 °C),high potentials (~0.6–1.0 V), and high oxygen concentration.Thecorrosionofthecarbonsupportsubsequentlyleadstothedetachmentofnoblemetalnanoparticles (NPs) fromthe sup‐port,resultinginaggregationofnoblemetalPNs,andthenthe

catalytic activity decreases. Furthermore, oxidation of carboncanchangethesurfacehydrophobicityofthesupportthatcanhindergastransport[2].

Thefollowingtwostrategiescanbeusedtomitigatecarboncorrosion:(1)graphitizationofcarbonblackand(2)alternativeuseofamorestablecarbonsupport.Graphitizationofcarbonplaysan important role in improving theelectrochemical sta‐bility of the support [3]. Higher amounts of graphitic carbonleadtoreductionofdefectsitesonthecarbonstructurewherecarbonoxidationoccurs[4].Graphitizationcanbeachievedbyheating carbon materials in protective gas at a high temp‐erature(≥1600°C)[5,6].Graphitizationaffordsthefabricationofmaterialswithhighresistancetooxidationandcorrosionbutwith reduced numbers of surface oxygen‐containing groups.The latter will accordingly affect metal deposition on thegraphitizedcarbonsupport [7].The second strategy to allevi‐

*Correspondingauthor.Tel:+86‐27‐87651837;Fax:+86‐27‐87879468;E‐mail:msc@whut.edu.cn ThisworkwassupportedbytheNationalNaturalScienceFoundationofChina(51372186),theNationalBasicResearchProgramofChina(973Pro‐gram,2012CB215504),andtheNaturalScienceFoundationofHubeiProvinceofChina(2013CFA082).DOI:10.1016/S1872‐2067(14)60211‐4|http://www.sciencedirect.com/science/journal/18722067|Chin.J.Catal.,Vol.36,No.4,April2015

HuiWuetal./ChineseJournalofCatalysis36(2015)490–495 491

ating carbon corrosion involves the use of carbon supportswithhigherstability.Recently,graphenenanosheets(GNS),astwo‐dimensional layers of sp2‐bonded carbon, have attractedconsiderable attention owing to their high surface area, re‐markable mechanical stiffness, excellent conductivity, andchemicalandelectrochemicalstabilities[8–10]forapplicationincatalystsupports[11,12].However,GNStendtoagglomerateor restack through van derWaals interactions [9,10], consid‐erablyloweringthesurfaceareaandlimitingpermeationoftheelectrolyte between the graphene layers, consequently de‐creasing the active surface area. These severely restrict theapplicationofGNS[13–15].ManyattemptshavebeenmadetoinhibittherestackingofGNSthroughsurfacefunctionalization[16–18], electrostatic stabilization [19], and synthesis of gra‐phenecompositesconsistingofsecondarybuildingblockssuchascarbonblack,carbonnanotube,andconductivenanoceram‐ic [13,14,20].Recently,ourgroup reporteda facilemethod topreparegraphenefroma‐Si1–xCxora‐Ti1–xCxnanofilmsusingachlorinationmethodundermildprocessingconditions[21,22].As reported, graphene can exist as graphene‐amorphous car‐bon (GNS@a‐C) core‐shell structures, which can afford in‐creased corrosion resistance for high electrochemical perfor‐mance[21].

Herein, for the first time,we report a core‐shell GNS@a‐Ccompositepreparedbyachlorinationmethodanduseditasasupport of Pt NPs for oxygen reduction reaction (ORR). Thecore‐shell structure not only inhibits the restacking of GNSmentioned earlier, but also restricts the corrosion of theamorphouscarboncoreundertheharshoperatingconditionstypically used in PEMFCs. Comparison between the currentPt/GNS@a‐Ccatalystand thecommercialPt/Ccatalyst showsthattheformerhasagoodcatalyticactivityandaremarkablyhighstability.

2. Experimental

2.1. Preparationofcore‐shellGNS@a‐CcompositesandPt/GNS@a‐Ccatalysts

Silicon carbide (SiC) samples (where the shell and core isamorphousandcrystallineSiC,respectively)withNano‐shells/films bought fromKaierNanoCo. andused as receivedwereplaced inahorizontalhot‐wall tubular flowreactoroperatingatambientpressures.Then, thereactorwasheated to800 °Cunder pure He and subsequently exposed to a He/Cl2 atmo‐spherefor1h.Thereactionwasstoppedbyflushingthereac‐torwithpureHegasat800 °C for1h toremoveresidualCl2andby‐products.Thefurnacewascooledto25°CunderpureHe,andthentheGNS@a‐Cwasobtained.

H2PtCl6·6H2O(SinopharmChemicalReagentCo.,Ltd.)solu‐tion,whichwasusedasaPtprecursor,wasaddeddropwisetotheGNS@a‐Csuspensionundervigorousstirring.ThepHofthesolutionwasadjustedto10–12using1.0mol/LNaOHaqueoussolution,andthenthemixturewasheatedunderrefluxat150°Cfor3–4htoensurecompleteformationofPtNPs.Followingstirring overnight, themixturewas filtered andwashedwithde‐ionizedwater.Theobtainedcatalystwasdriedinavacuum

ovenat80°Cfor8h.Forcomparisonpurposes,acommercialPt/C catalyst (20 wt % Pt supported on carbon black) waspurchasedfromJohnsonMatthey.

2.2. Characterization

MorphologiesofthesupportandcatalystwereanalyzedonaJEOL2100high‐resolutiontransmissionelectronmicroscope(HRTEM), operating at 10 kV. Raman spectroscopywas perf‐ormed on a Renishaw using Ar ion laser with an excitationwavelength of 514.5 nm. X‐ray diffraction (XRD)was perfor‐medon aRigakuX‐ray diffractometer equippedwith a CuKαradiation source.XRDpatternswere collectedusing a stepof0.01° and a count time of 2 s per step within a 2θ range of10°–90°.

Electrochemicalstudieswereconductedusingacomputer‐controlled Autolab PGSTAT 30 potentiostat (Eco Chemie B.V,Holland)withathree‐electrodecellsetup.Asaturatedcalomelelectrode was used as the reference electrode and platinumwirewasusedasthecounterelectrode.However,inthispaper,all potentials are expressedon the scaleof the reversible hy‐drogen electrode (RHE). The electrolyte solution (0.1 mol/LHClO4)waspurgedusinghigh‐purityN2for30minpriortoanyelectrochemicalmeasurements. The sample (3mg)was disp‐ersed in the stock solution (1000 L) that was prepared bymixing isopropanol (600L)withpurewater(380L)and5wt%Nafionionomersolution(20L;DuPontCo.,Ltd.).Then,theformedinkwascoatedonamirror‐polishedglassycarbondisk electrode as a working electrode. The electrochemicalerosion(ECE)ofthesupportwasassessedataconstantpoten‐tialof1.2Vasa functionoftimetovarytheECErates.Cyclicvoltammogramsintherangeof0–1.2Vwererecordedperiod‐icallybeforeandaftertheECEtestataconstantscanrateof50mV/s. An electrochemical‐accelerated durability test (ADT)wasconductedbycyclicvoltammetry(CV)analysisperformedat 0.6–1.2 V for 4000 cycles. CVs were recorded before andafterADTfrom0to1.2Vatascanrateof50mV/s.Finally,theORR activity of the catalystswas assessed in anO2‐saturated0.1mol/LHClO4solutionona rotatingdiskelectrodesystem.Polarization curves were obtained at room temperature at ascan rate of 10mV/s and a rotation rate of 1600 r/min, rec‐ordedfrom1.1to0.2V.

3. Resultsanddiscussion

3.1. StructuralandelectrochemicalpropertiesofGNS@a‐Ccomposites

Asobserved inFig.1(a),afterchlorination, theamorphouscarbonNPswerecoveredwithafewlayersofGNS,resultingina core‐shell GNS@a‐C architecture. Crystal residues of β‐SiCwerenotobservedafterchlorination,indicatingthenear‐com‐plete transformation of SiC into nanoporous carbide‐ derivedcarbon (CDC) matrix and graphene shells (Fig. 1(b)). Fig. 2showstheRamanspectrumofthefinalsiliconcarbide‐derivedcarbon (SiC‐CDC).Theoccurrenceofa2Dpeakand two rela‐tivelybroadDandGpeaksat1320and1580cm−1indicatesthe

492 HuiWuetal./ChineseJournalofCatalysis36(2015)490–495

presenceoforderedgraphiticdomainsinthea‐Si1–xCxnetwork[23,24], thereby confirming the successful transformation ofa‐Si1–xCx nanoshell on the crystalline SiC NPs into graphenenanoshell. The D band was associated with the presence ofdefectsandstagingdisorderofgrapheneandamorphouscar‐bon,andtheGbandcouldbeusedtoinvestigatethedegreeofgraphitization.Asnoted in the followingdiscussion, thepres‐enceofdefectsongrapheneisconducivetotheadsorptionofPtNPs on the support. Therefore, a‐Si1–xCx nanoshellswere suc‐cessfullyconvertedintographeneonsurfacesofβ‐SiCNPsbychlorination, while the β‐SiC core was converted into amor‐phouscarbon.

ECE test was conducted to investigate the stability ofGNS@a‐C.Theresultswereconsistentwiththatfromourpre‐vious work [21]. Fig. 1(c) and (d) present the CV curves ofGNS@a‐C and commercial Vulcan XC‐72 carbon, respectively.Thepotentialwindowbetween0.3and0.8Visanindicatorofcapacitive current, which depends on the electrochemicallyaccessible area for diffusion of the electrolyte to the internalmicropores of the carbon matrix. Relative to XC‐72 carbonblack, GNS@a‐C shows a considerably higher electric double‐layer capacitance, indicative of a higher specific surface areaand greater accessibility to the electrolyte and charged ions.For both samples, the peaks between 0.6 and 0.8 Vwere at‐tributed to the oxidation–reduction of graphene that becamemoreprominentwithincreasingECEtreatmenttimesupto24h.Theincreaseinthepeakintensitycanbeascribedtothepres‐enceofsurfacedefectsthataggravatedthecorrosionofcarbon.After24h,theoxidationpeakintensityofXC‐72increasedwithtime, whereas that of GNS@a‐C decreased. This finding sug‐

gests that GNS@a‐C features higher corrosion resistance andimproved electrochemical stability owing to the presence ofgraphenelayersthatpreventscorrosionofamorphouscarbon.

3.2. StructuralandelectrochemicalpropertiesofPt/GNS@a‐Ccatalysts

PowderXRDanalysis(Fig.3)wasconductedtocomparethestructures of GNS@a‐C, XC‐72, commercial Pt/C, and Pt/GNS@a‐C.Thepeakat24.5°wasattributedtothe(002)carbonplaneofXC‐72.Incontrast,the(002)peakofGNS@a‐Cshiftedtoalowerangle(21.5°)relativetothatofXC‐72whichcouldbeattributedtothesynergeticeffectbetweengrapheneandamor‐phous carbon. Following chlorination, distinct crystalline SiCresiduesorcrystallinegraphitewasnotobserved,indicatinganear‐complete transformation of β‐SiC into carbon includingamorphous carbon and graphene. The peaks at 2θ= 30°–90°were indexed to Pt crystals with face‐centered cubic (fcc)structures.Thepeaksat39.7°,46.5°,67.7°,and81.4°wereas‐signed to the (111), (200), (220), and (311) planes of Pt, re‐spectively.

Fig. 4 shows themicrostructuresofPt/GNS@a‐CandPt/Ccatalysts.ThelatticeplanesofPt/GNS@a‐Cwithspacingof0.35and0.22nmwereattributedtographeneandPt(111),respec‐tively.Additionally, Fig. 4(a) and (c) (inset) show theparticlesize histograms of the catalyst samples as determined from

~0.35 nmgraphene

amorphous carbon

~0.35 nmgraphene

(a) (b)

0.0 0.2 0.4 0.6 0.8 1.0 1.2-3-2-101234567

Cur

rent

den

sity

(m

A/c

m2 )

Potential (V vs. RHE)

0 h 12 h 24 h 48 h 72 h

(c)

0.0 0.2 0.4 0.6 0.8 1.0 1.2-0.8-0.6-0.4-0.20.00.20.40.60.81.01.21.4

Cur

rent

den

sity

(m

A/c

m2 )

Potential (V vs. RHE)

0 h 12 h 24 h 48 h 72 h

(d)

Fig.1. (a,b)HRTEMimagesofGNS@a‐C.CVplotsofGNS@a‐CNPs(c)andcommercialcarbonblack(VulcanXC‐72)(d)recordedat1.2V(vs.RHE)asa functionof time(0.1mol/LHClO4, scanrate:50mV/s) forelectrochemicalerosionevaluation.

1000 1500 2000 2500 3000

Inte

nsity

Raman shift (cm1)

D

G

2D

Fig.2.Ramanspectrumofa‐C@GNSNPs.

10 20 30 40 50 60 70 80 90

(4)

(3)

(2)

Pt(220) Pt(311)Pt(200)

Inte

nsit

y

2/( o )

C(002)

Pt(111)

(1)

Fig. 3. XRD patterns of XC‐72 (1), GNS@a‐C (2), Pt/C (3), andPt/GNS@a‐C(4).

HuiWuetal./ChineseJournalofCatalysis36(2015)490–495 493

TEM images. Commercial Pt/C catalyst sample (Fig. 4(c) and(d))featuredPtNPswithanaveragesizeof3.2nm;someareasfeaturingaggregatedPtNPswereadditionallypresent,reveal‐ingtheinhomogeneousdistributionofthecatalystparticles.Incontrast, Pt NPs were well dispersed on GNS (Pt/GNS@a‐C)withanaveragediameterof2.8nmandaverynarrowparticlesizedistribution.ThesurfacedefectsonGNSservedasanchor‐ingsitesforthePtprecursortopreventaggregationofPtNPs.Smallercatalystparticlesarebelievedtodisplaybettercatalyticactivities relative to larger catalyst particles introduced at agivencontent.

Fig.5 showsCVcurvesofbothcatalysts recordedat roomtemperature. All voltammograms display a two‐peak reduc‐tion‐oxidation/adsorption‐desorptionfeature.Thefirstpeakat0.04–0.3VwasattributedtotheadsorptionanddesorptionofhydrogenonPt,andthesecondpeakat0.5–1.2VwasascribedtotheoxidationandreductionofPtmetal.Theelectrochemicalspecificarea(ECSA)ofthecatalystsampleswascalculatedbymeasuring the charge collected within the hydrogen adsorp‐tion–desorption region following double‐layer correction andassumingavalueof210μC/cm2foradsorptionontoahydro‐genmonolayer[25,26].AsdeterminedinFig.5(a),theECSAofPt/GNS@a‐C (90.1m2/g) was higher than that of Pt/C (79.2m2/g).BasedonthepolarizationcurvesforORRofthesecata‐lystsinFig.5(b),Pt/GNS@a‐Cfeaturedasimilarhalf‐wavepo‐tential(0.83V)tothatofPt/C(0.81V).Diffusion‐limitingcur‐rents were obtained in the potential region below 0.6 V,whereasamixedkinetic‐diffusioncontrolregionwasobservedbetween0.7and0.9V.ThekineticcurrentwascalculatedfromtheORRpolarization curve at 0.9V vs.RHE according to theKoutecky‐Levichequation[27].ThemassactivityofPt/GNS@a‐C (0.121 A/mg) was nearly twice as high as that of Pt/C(0.064 A/mg), demonstrating the higher ORR activity of

Pt/GNS@a‐CcomparedwiththatofPt/C.The improvedECSAandORRactivitycouldbeattributed to theoptimizeddisper‐sion and size distribution of Pt NPs, and the good electricalconductivityofGNS.

AsshowninFig.6(a)and(b),bothcatalystsdisplayedade‐crease in thehydrogen adsorption region followingADT.TheretainedECSA,asnormalizedwiththeinitialECSA,wasplottedas a function of cycle number in Fig. 6(c). After 4000 cycles,53% of the initial ECSA of Pt/GNS@a‐C was maintained,whereas only 35%of the initial ECSAwaspreserved inPt/C,therebydemonstrating that Pt deposited onGNS@a‐C is con‐siderablymorestablethanthatdepositedoncarbonunderthesametestingconditions.TheORRactivitiesofPt/GNS@a‐CandPt/CbeforeandafterADTare shown inFig.6(d).After4000cycles, Pt/C displayed 91mV negative shift of the half‐ wavepotential.Incontrast,Pt/GNS@a‐Conlydisplayeda31mVneg‐ative shift. The mass activity of Pt/C changed from 0.064 to0.010A/mg,correspondingtoadecreaseof84.4%.Incontrast,themassactivityofPt/GNS@a‐Cchangedbyonly66.7%.

Tofurthersubstantiatethedifferenceindegradationbetw‐eenPt/GNS@a‐CandPt/C,bothcatalystswereinvestigatedbyHRTEMafterADT.Fig.7showstheTEMimagesofthecatalystsandtheassociatedPtsizehistograms.Slightagglomerationofthe Pt NPs was observed for Pt/GNS@a‐C that displayed anincreased average particle size from 2.8 to 4.8 nm followingADT(Fig.7(a)and(c)).Bycontrast,moresevereagglomerationofthePtNPswasobservedforPt/CafterADT(Fig.7(b)),andthemean size increased to 5.2 nm after the potential cyclingtest (Fig. 7(d)). The high stability of Pt/GNS@a‐C relative tothatofPt/Cdemonstratesthatthegraphenelayeriseffectivein

~0.22nm Pt(111)

~0.35nmgraphene

(a) (b)

~0.22nm Pt(111)

(c) (d)

Pt/ GNS @ a-C

2.8nm2.8 nm

05

1015202530354045

2.0 2.5 3.0 3.5 4.0 4.5

Nu

mb

er

(%)

Particle size (nm)

Pt/GNS@a-C

Pt/C3.2nm3.2 nm

2.5 3.0 3.5 4.0 4.5Particle size (nm)

5.0 5.505

10152025303540

Nu

mb

er (

%) Pt/C

Fig.4.TEMimagesofPtNPssupportedonGNS@a‐C(a,b)andXC‐72(c,d).

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4-0.6-0.5-0.4-0.3-0.2-0.10.00.10.20.30.4

0.4 0.6 0.8 1.0

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

Cur

rent

den

sity

(m

A/(g

Pt c

m2 ))

Potential (V vs. RHE)

(a)

Pt/C

Pt/GNS@a-C

Pt/GNS@a-C

Pt/C

Cur

rent

den

sity

(m

A/(g

Pt c

m2 ))

Potential (V vs. RHE)

(b)

Fig.5.CVcurvesofPt/CandPt/GNS@a‐C(a);Current‐potential‐polar‐izedcurvesforORR(b).

494 HuiWuetal./ChineseJournalofCatalysis36(2015)490–495

inhibiting the migration and aggregation of Pt NPs, and in‐creasingtheresistanceofthesupporttoelectrochemicalcorro‐sion.However,forPt/C,themigrationandagglomerationofPtNPson thesurfaceofcarbonblackarepredominantlycausedbythecorrosionofcarbonsupportsandtheOstwaldripeningofPtNPsthatlowerstheelectrochemicalactivityofthecatalyst[27].

4. Conclusions

Core‐shell GNS@a‐C composites were successfully synthe‐sizedbyachlorinationmethodandusedasthesupportforPtnanoparticles.ThePt/GNS@a‐CcatalystdisplayedsignificantlyenhancedactivityandstabilityrelativetothecommercialPt/Ccatalyst. The improved activity was attributed to the goodconductivity of graphene that was also effective in inhibitingmigrationandaggregationofPtnanoparticlesbycoveringthe

amorphouscarboncore,aswellasprotectingthecarbonfromchemical and electrochemical corrosion. The present findingsdemonstrated the GNS@a‐C composite as a highly efficientcatalyst support possesses great potential application in fuelcellsandotherindustrialfields.

References

[1] KinoshitaK.Carbon:Electrochemical andPhysicochemicalProp‐erties.NewYork:wiley,1988

[2] YuXW,YeSY.JPowerSources,2007,172:133[3] StevensDA,HicksMT,HaugenGM,DahnJR.JElectrochemSoc,

2005,152:A2309[4] ShaoYY,YinGP, Zhang J, GaoY Z.ElectrochimActa, 2006,51:

5853[5] Coloma F, Sepulvedaescribano A, Rodriguezreinoso F. J Catal,

1995,154:299[6] BomD,AndrewsR,JacquesD,AnthonyJ,ChenB,MeierMS,Sele‐

0.2 0.4 0.6 0.8 1.0

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

0.6

0.4

0.2

0.0

-0.2

-0.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0 1000 2000 3000 40000.0

0.2

0.4

0.6

0.8

1.0

Cur

rent

den

sity

(m

A/(g

Pt c

m2 ))

Pt/ GNS@a-C before 4000C Pt/GNS@a-C after 4000C Pt/C before 4000C Pt/C after 4000C

31 mV

93 mV

(d)

Potential (V vs. RHE)

Cur

rent

den

sity

(m

A/(g

Pt c

m2 ))

Potential (V vs. RHE)

Cur

rent

den

sity

(m

A/(g

Pt c

m2 ))

(a) 0C 100C 200C 300C 400C 500C 1000C 2000C 3000C 4000C

Potential (V vs. RHE)

0C 100C 200C 300C 400C 500C 1000C 2000C 3000C 4000C

(b)

Pt r

elat

ive

surf

ace

(vs.

inti

al)

Number of potential cycles

Pt/GNS@a-C Pt/C

(c)

Fig.6.CVcurvesofPt/GNS@a‐C(a)andPt/Ccatalysts(b)beforeandaftercycling;VariationinECSA,relatedtothePtcatalyticsurfacearea,asafunctionofthecyclenumber(c);ORRonPt/GNS@a‐CandPt/Cbeforeandafter4000cyclesat1600r/min(0.1mol/LHClO4,scanrate10mV/s)(d).

(a)

3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.50

5

10

15

20

25

30

Pt/GNS@a-C

Num

ber

of p

oten

tial

(%

)

Partical size (nm)

4.8 nm(b) (c)

3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.00

5

10

15

20

25

Num

ber

of p

oten

tial

(%

)

Partical size (nm)

5.4 nm(d)

Fig.7.HRTEMimagesofPt/GNS@a‐C(a)andPt/C(c)catalystsafterADT;AssociatedPtparticlesizedistributionsofPt/GNS@a‐C(b)andPt/C(d)catalysts.

HuiWuetal./ChineseJournalofCatalysis36(2015)490–495 495

gueJP.NanoLett,2002,2:615[7] HeCZ,DesaiS,BrownG,BollepalliS.ElectrochemSoc interface,

2005,14(3):41[8] GeimAK,NovoselovKS.NatMater,2007,6:183[9] LiD,MullerMB,GiljeS,KanerRB,WallaceGG.NatNanotechnol,

2008,3:101[10] StankovichS,DikinDA,DommettGHB,KohlhaasKM,ZimneyEJ,

StachEA,PinerRD,NguyenST,RuoffRS.Nature,2006,442:282[11] HeDP,ChengK,PengT,PanM,MuSC.JMaterChemA,2013,1:

2126[12] WuP,LüHF,PengT,HeDP,MuSC.SciRep,2014,4:3968[13] ZhaoX,HaynerCM,KungMC,KungHH.ACSNano,2011,5:8739[14] RaoCNR,SoodAK,VogguR, SubrahmanyamKS. JPhysChem

Lett,2010,1:572[15] DuXS,YuZZ,DasariA,MaJ,MoMS,MengYZ,MaiYW.Chem

Mater,2008,20:2066[16] ZuSZ,HanBH.JPhysChemC,2009,113:13651[17] HeDP,KouZK,XiongYL,ChengK,ChenX,PanM,MuSC.Carbon,

2014,66:312[18] HeDP,ChengK,LiHG,PengT,XuF,MuSC,PanM.Langmuir,

2012,28:3979[19] YangXY,DouX,RouhanipourA,ZhiLJ,RaderHJ,MullenK.JAm

ChemSoc,2008,130:4216[20] FanZJ,YanJ,ZhiLJ,ZhangQ,WeiT,FengJ,ZhangML,QianWZ,

WeiF.AdvMater,2010,22:3723[21] PengT,LvHF,HeDP,PanM,MuS.C.SciRep,2013,3:1148[22] PengT,KouZK,WuH,MuSC.SciRep,2014,4:5494[23] BullotJ,SchmidtMP.PhysStatusSolidiB,1987,143:345[24] MorimotoA,KataokaT,KumedaM,ShimizuT.PhilosMagB,1984,

50:517[25] SchmidtTJ,GasteigerHA,StäbGP,UrbanPM,KolbDM,BehmR

J.JElectrochemSoc,1998,145:2354[26] ColombiCiacchiL,PompeW,DeVitaA.JPhysChemB,2003,107:

1755[27] LimB,JiangMJ,CamargoPHC,ChoEC,TaoJ,LuXM,ZhuYM,

XiaYN.Science,2009,324:1302

应用于氧还原反应的石墨烯-无定形碳核壳结构复合材料载铂催化剂

吴 惠, 彭 焘, 寇宗魁, 张 建, 程 坤, 何大平, 潘 牧, 木士春*

武汉理工大学材料复合新技术国家重点实验室, 湖北武汉430070

摘要: 采用氯化法制备石墨烯-无定型碳复合材料(GNS@a-C), 并用作质子交换膜燃料电池(PEMFC)氧还原反应Pt催化剂的载体.

结果显示, 所制Pt/GNS@a-C催化剂与传统商业催化剂Pt/C相比, 有较好的活性和较高的稳定性: 质量活性(0.121 A/mg)几乎是

Pt/C (0.064 A/mg)的两倍. 更重要的是, 该新型催化剂加速4000圈后其电化学活性面积保留了最初的51%,与Pt/C的33%相比, 前者

有更好的电化学稳定性, 显示它在PEMFC中将具有较好的应用潜力.

关键词: 低温燃料电池; 载体; 核壳结构; 氧还原反应

收稿日期: 2014-07-12. 接受日期: 2014-08-22. 出版日期: 2015-04-20.

*通讯联系人. 电话: (027)87651837; 传真: (027)87879468; 电子信箱: msc@whut.edu.cn

基金来源: 国家自然科学基金(51372186); 国家重点基础研究发展计划(973计划, 2012CB215504); 湖北省自然基金重点项目(2013-

CFA082)

本文的英文电子版由Elsevier出版社在ScienceDirect上出版(http://www.sciencedirect.com/science/journal/18722067).

GraphicalAbstract

Chin.J.Catal.,2015,36:490–495 doi:10.1016/S1872‐2067(14)60211‐4

Core‐shellgraphene@amorphouscarboncompositessupportedplatinum catalystsforoxygenreductionreaction

HuiWu,TaoPeng,ZongkuiKou,JianZhang,KunCheng,DapingHe,MuPan,ShichunMu*

WuhanUniversityofTechnology

Core‐shell graphene nanosheets@amorphous carbon (GNS@a‐C) composite, as ahighlyefficientcatalystsupport,displaysexcellentoxygenreductionreactionactivityandhighelectrochemicalstability.