Pd7Ir1433

HighperformanceofacarbonsupportedternaryPdIrNicatalystforethanolelectro-oxidationinanion-exchangemembranedirectethanolfuelcellsShuiyunShen,T.
S.
Zhao,*JianboXuandYinshiLiReceived21stOctober2010,Accepted6thJanuary2011DOI:10.
1039/c0ee00579gInthispaper,wereportthesynthesisofacarbonsupportedternaryPdIrNicatalystfortheethanoloxidationreactioninanion-exchangemembranedirectethanolfuelcells(AEMDEFCs).
WedemonstratethattheuseoftheternaryPdIrNicatalystattheanodeofanAEMDEFCcanincreasethepeakpowerdensitybymorethan122%ascomparedwiththeuseofthemonometallicPdcatalyst,69%ascomparedwiththeuseofthebimetallicPdIrcatalyst,and44%ascomparedwiththeuseofthebimetallicPdNicatalyst.
CyclicvoltammetryandchronopotentiometryanalysesprovethattheternaryPdIrNicatalystiscatalyticallymuchmoreactiveandmorestablethanthemonometallicPdcatalystandthebimetallicPdIrandPdNicatalysts.
1.
IntroductionAnimportantadvantageofanion-exchangemembranedirectalcoholfuelcells(AEMDAFCs)isthatthekineticsofbothalcoholanodicoxidationandoxygencathodicreductioninalkalinemediabecomemuchfasterthaninacidicmedia,makingitpossibletousenon-platinumandlow-costmetalcatalysts.
1,2AmongvariouspossiblefuelsforAEMDAFCs,includingmethanol,ethanol,glycerol,ethyleneglycol,andsoon,ethanolisthebestchoice,asithasahigherenergydensitythanmethanol(8.
0kWhkg1vs.
6.
1kWhkg1),islesstoxicandcanbeproducedinlargequantitiesfromagriculturalproductsorbiomass.
3,4Theuseofpalladiumastheanodecatalystfortheethanoloxidationreaction(EOR)inanion-exchangemembranedirectethanolfuelcells(AEMDEFCs)offerstwosignicantadvan-tagesascomparedwiththeuseofPt.
5,6First,PdshowsbothahighercatalyticactivityandbetterstabilityfortheEORinalkalinemediathanPtdoes.
Secondly,PdismoreabundantthanPtandhasamuchlowerprice,andthusthecostoffuelcelltechnologycanbegreatlyreduced.
However,itisworthnotingthatwithstate-of-the-artanodecatalysts,ethanolisselectivelyoxidizedtoacetateinalkalinemediathroughafour-electronpathwayaccordingto7–10C2H5OH+5OH/CH3COO+4H2O+4e(1)Combiningcyclicvoltammetry(CV)withinsituFouriertransforminfraredspectroscopy,Zhouetal.
8conrmedthatina0.
1MNaOHsolutioncontaining0.
1Methanol,theselec-tivityforethanoloxidationtoCO2wasaslowas2.
5%inthepotentialrangingfrom0.
60Vto0.
0Vvs.
SCE.
Bambagionietal.
9,10employedionicchromatograpyand13C{1H}NMRspectroscopytoanalyzetheanodeexhaustfromAEMDEFCswithPd/MWCNT,Pd/CandPd–(Ni–Zn)/Castheanodecatalyst,respectively,andtheresultsshowedthatduringtheDepartmentofMechanicalEngineering,TheHongKongUniversityofScienceandTechnology,ClearWaterBay,Kowloon,HongKongSAR,China.
E-mail:metzhao@ust.
hk.
Fax:(+852)23581543;Tel:(+852)2358647BroadercontextRecently,attentionhasbeenfocusedontheuseofpalladium(Pd)astheanodecatalystfortheethanoloxidationreaction(EOR)inanion-exchangemembranedirectethanolfuelcells(AEMDEFCs),asPdofferstwosignicantadvantagesascomparedwiththeuseofPt.
First,PdshowsbothahighercatalyticactivityandbetterstabilityfortheEORinalkalinemediathanPt.
Secondly,PdismoreabundantthanPtandhasamuchlowerprice,andthusthecostoffuelcelltechnologycouldbegreatlyreduced.
However,boththecatalyticactivityandstabilityofPdfortheEORinalkalinemedianeedtobefurtherimproved.
Inthisstudy,ahigh-performancecarbonsupportedternaryPdIrNicatalystwassynthesizedfortheEORinalkalinemedia.
InthePdIrNicatalyst,Pdfacilitatesethanoldehydrogenation,whiletheIrandNispeciesconcurrentlycontributetotheremovalofadsorbedethoxyintermediates.
TheuseoftheternaryPdIrNicatalystattheanodeofanAEMDEFCresultsinmuchhigherperformancethantheuseofboththemonometallicPdandbimetallicPdIrandPdNicatalysts.
1428|EnergyEnviron.
Sci.
,2011,4,1428–1433ThisjournalisTheRoyalSocietyofChemistry2011DynamicArticleLinksC1433|1429theanodeelectrode,ananodeinkwasrstpreparedbymixingthePd/C,Pd2Ni3/C,Pd7Ir/CorPd7IrNi12/Ccatalystwith5wt.
%PTFEemulsionasabinderinethanol.
Afterultrasonication,thewelldispersedinkwasbrushedontoanickelfoam(HohsenCorp.
,Japan),whichservedasthebackinglayeroftheanodeelectrode.
Themetal(PdandIr)loadingintheanodewas1.
0mgcm2.
Thecellperformancetestswerecarriedoutat60C,andfuelsolutionwaspumpedtotheanodeatarateof1.
0mlmin1,anddrypureoxygenataowrateof100standardcubiccenti-metersperminute(sccm)wasfedtothecathode.
Thecellperformancedatawerecollectedafteritbecamestable.
3.
Resultsanddiscussion3.
1XRD,TEMandXPScharacterizationThebulkstructuralinformationofthePd7IrNi12/CcatalystwasobtainedbyXRDandisshowninFig.
1.
Therstpeaklocatedatthe2qvalueofabout25referstothegraphite(002)facetofthecarbonpowdersupport.
Thediffractionpeaksatthe2qvaluesof40.
6,47.
06,68.
5,and82.
40areassignedtothe(111),(200),(220)and(311)facetsoftheface-centeredcubic(fcc)crystallinestructure,respectively,andthesefourpeaksarelocatedathigher2qvalueswithrespecttothatofpurePd(JCPDS46-1043),whileatlower2qvalueswithrespecttothatofpureIr(JCPDS06-0598),andthiscanbeattributedtotheincorporationofalowerdspacecrystalstructureofIr(d1112.
217)thanthatofPd(d1112.
246),suggestingtheformationofPdIralloy.
Therealsoexistsanothersmallpeakatthe2qvalueof60.
0,correspondingtotheNi(OH)2(110)facet.
12However,nosinglepeakisobservedatthe2qvalueofabout33.
5fortheNi(OH)2(100)facetinthePd7IrNi12/CcatalystduetosuperpositionofthediffractionpeakofthePd(111)facet,whichiswiderthanthatinthePdNi/Ccatalysts.
12Thisisbecausecitratewasusedasacomplexingagentandstabilizerduringthecatalystsynthesis,andthisresultedinasmallercrystallitesizeofthemetalparticlesonthePd7IrNi12/Ccatalyst.
TheaveragecrystallitesizeofthemetalparticlesonthePd7IrNi12/Ccatalystiscalculatedbasedonthebroadeningofthe(111)diffractionpeaksaccordingtoScherrerequation15d0:9lB2qcosqmax(4)wherelrepresentsthewavelengthoftheX-ray,qistheangleofthemaximumpeak,andB2qisthewidthofthepeakatthehalfheight.
AccordingtotheScherrerequation,theaveragecrystal-litesizeofthemetalparticlesonthePd7IrNi12/Ccatalystis2.
7nm.
Fig.
2showstheTEMimageandhistogramofthemetalparticlesizedistributionofthePd7IrNi12/Ccatalyst.
InFig.
2a,itcanbeobservedthatthemetalparticlesonthePd7IrNi12/Ccatalystexhibitasphericalshapeandarewelldispersedonthecarbonpowdersupportwithoutsevereaggregation.
ThemetalparticlesizedistributionofthePd7IrNi12/Ccatalystwasevalu-atedfromanensembleof200particles.
Basedonthisevaluation,thePd7IrNi12/Ccatalystshowsametalparticlesizedistributionrangingfrom1.
0to4.
6nm,andtheaveragemetalparticlesizeis2.
6nm,whichisalmostthesameasthevaluepredictedfromtheXRDdata.
TheXPStestwasemployedtoanalyzethesurfacecompositionandoxidationstateofthemetalsonthePd7IrNi12/Ccatalyst.
BasedontheintensitiesofXPSpeaks,thesurfaceatomicratioofFig.
1XRDpatternsofthePd7IrNi12/Ccatalyst,JCPDS46-1043leforPd(solidlines)andJCPDS06-0598leforIr(dashedlines).
Fig.
2TEMimage(a)andhistogramofmetalparticlesizedistribution(b)ofthePd7IrNi12/Ccatalyst.
1430|EnergyEnviron.
Sci.
,2011,4,1428–1433ThisjournalisTheRoyalSocietyofChemistry2011Pd:Ir:NiforthePd7IrNi12/Ccatalystis6:1:8,whichshowssomedeviationfromthenominalratiosintheprecursors.
TheIr4fXPSandNi2pXPSspectraofthePd7IrNi12/Ccatalystare,showninFig.
3aandb.
InFig.
3a,itcanbeobservedthatthereexiststhreepeaks;thepeakat68.
0eVcanbeassignedtoNi3p,32whiletheothertwopeakscorrespondtoIr4f,consistingofahighenergyband(Ir4f5/2)at64.
0eVandalowenergyband(Ir4f7/2)at61.
0eV.
33TheIr4fspectrumcanbedeconvolutedintotwodoublets,correspondingtometallicIrandIrO2,respectively;theXPSarearatiosforIrandIrO2are78.
2%and21.
8%.
InFig.
3b,takingtheshake-uppeaksintoaccount,theNi2pspectrumcanbedeconvolutedintofourdoublets,correspondingtometallicNi,NiO,Ni(OH)2andNiOOH;34theXPSarearatiosforthemare4.
8%,5.
9%,62.
0%,and27.
3%,respectively.
3.
2ElectrochemicalpropertyandcellperformanceFig.
4ashowsthestabilizedCVcurves(the20thcycle)oftheEORonthePd/C,Pd2Ni3/C,Pd7Ir/CandPd7IrNi12/Ccatalystsmeasuredinthepotentialrangingfrom0.
926Vto0.
274V;Fig.
4bshowsonlythepositivedirectionscansforclearobservation.
Thescanratewas50mVs1.
AsshowninFig.
4b,boththebimetallicPd2Ni3/CandPd7Ir/CcatalystsshowahighercatalyticactivitythanthemonometallicPd/Ccatalystdoes,andthePd7IrNi12/CcatalystshowsthehighestcatalyticactivityfortheEORinalkalinemediaamongallthecatalysts,intermsofboththeonsetpotentialandthepeakcurrentdensity.
TheonsetpotentialoftheEORonthePd7IrNi12/Ccatalystis0.
71V,0.
59VonPd/C,0.
68VonPd2Ni3/Cand0.
68VonPd7Ir/C;thepeakcurrentdensityoftheEORonthePd7IrNi12/Ccatalystis0.
139Acm2,0.
101Acm2onPd/C,0.
136Acm2onPd2Ni3/Cand0.
103Acm2onPd7Ir/C.
ItisnotedthatcomparedtothePd/Ccatalyst,thePd7Ir/Ccatalystischaracterizedwithamorenegativepeakpotential,thePd2Ni3/Ccatalystischaracterizedwithahigherpeakcurrentdensity,whilebothamorenegativepeakpotentialandahigherpeakcurrentdensityforthePd7IrNi12/Ccatalyst.
AccordingtotheXPSresults,itcanbeconrmedthatthesurfacecompositionandoxidationstateofboththeIrandNispeciesonthePd7IrNi12/CcatalystarealmostthesameasthatinthebimetallicPdIrorPdNicatalysts,12,29andthisindicatesthataconcurrentpromotionfromtheadditionofIr,alongwithNi,accountsforthehighestcatalyticperformanceofthePd7IrNi12/CcatalystfortheEORinalkalinemedia:12,29IradditiontoPdcanfacilitatetheremovalofadsorbedethoxyintermediates,asthehydroxylgroupsaremoreeasilyadsorbedFig.
3Ir4fXPSspectrum(a)andNi2pXPSspectrum(b)ofthePd7IrNi12/Ccatalyst.
Fig.
4CVcurves(a)andpositivedirectionscans(b)oftheEORonthePd/C,Pd2Ni3/C,Pd7Ir/CandPd7IrNi12/Ccatalystsin1.
0MKOH+1.
0Methanol(scanrate:50mVs1).
ThisjournalisTheRoyalSocietyofChemistry2011EnergyEnviron.
Sci.
,2011,4,1428–1433|1431onmetallicIrandIrO2atlowerpotentials;thenickelhydroxides,themaincomponentoftheNispeciesinthePd7IrNi12/Ccatalyst,canfurthercontributetotheEORonPdinalkalinemediathroughareversibleredoxasshownineqn(1).
ThestabilityofthePd/C,Pd2Ni3/C,Pd7Ir/CandPd7IrNi12/CcatalystsfortheEORinalkalinemediawasalsoevaluatedbytheCPtest.
Fig.
5showstheCPcurvesoftheEORonthePd/C,Pd2Ni3/C,Pd7Ir/CandPd7IrNi12/Ccatalysts,inwhichaconstantcurrentdensityof20mAcm2wasappliedfor24000s.
AsshowninFig.
5,thepolarizationpotentialincreasesgrad-uallywithtimeandthroughallthescanningtimethePd7IrNi12/Ccatalystshowsthelowestpolarizationpotentialamongallthecatalysts.
Throughthetimerangingfrom100sto24000s,thePd7IrNi12/Ccatalysthasapotentialdegradationof40mV,whilstitis90mVforPd/C,55mVforPd2Ni3/Cand70mVforPd7Ir/C,indicatingthattheadditionofIr,alongwithNi,toPdcanconcurrentlyfacilitatetheremovaloftheadsorbedethoxyintermediates,hencemakingitmoreresistanttopoisoning.
Fig.
6showsthepolarizationandpower–densitycurvesoftheAEMDEFCwithPd/C,Pd2Ni3/C,Pd7Ir/CandPd7IrNi12/Castheanodecatalyst,andtheinsertisthespecicoperatingconditions.
AscanbeseeninFig.
6,theAEMDEFCwiththePd7IrNi12/Ccatalystastheanodeshowsthehighestperfor-mance.
Theopen-circuitvoltage(OCV)oftheAEMDEFCwiththePd7IrNi12/Ccatalystasanodeis0.
84V,whichis0.
18VhigherthanthatwithPd/C,0.
04VhigherthanthatwithPd2Ni3/C,and0.
14VhigherthanthatwithPd7Ir/C.
ThepeakpowerdensityoftheAEMDEFCwiththePd7IrNi12/Ccatalystasanodeis49mWcm2,whichis122%higherthanthatwithPd/C,44%higherthanthatwithPd2Ni3/Cand69%higherthanthatwithPd7Ir/C.
Fig.
7showsthepolarizationandpower–densitycurvesoftheAEMDEFCwithPd/C,Pd2Ni3/C,Pd7Ir/CandPd7IrNi12/Castheanodecatalystinamodest–highconcentra-tionofsolution,andtheinsertisthespecicoperatingcondi-tions.
FortheAEMDEFCwiththePd7IrNi12/Ccatalystasanode,theOCVis0.
90V,0.
095VhigherthanthatwithPd/C,0.
05VhigherthanthatwithPd2Ni3/C,and0.
04VhigherthanthatwithPd7Ir/C.
ThepeakpowerdensityfortheAEMDEFCwiththePd7IrNi12/Ccatalystastheanodeis92mWcm2,whichis58%higherthanthatwithPd/C,15%higherthanthatwithPd2Ni3/Cand28%higherthanthatwithPd7Ir/C.
4.
ConclusionsInthiswork,acarbonsupportedternaryPdIrNicatalystwithaPd:Ir:Niatomicratioof7:1:12wassynthesizedbythesimultaneousreductionmethod,andcomparedwiththemono-metallicPd/C,bimetallicPd2Ni3/CandPd7Ir/CcatalystsastheanodeinanAEMDEFC.
XPSanalysesshowedthatthesurfacecompositionandoxidationstateofbothIrandNispeciesonthePd7IrNi12/CcatalystwerealmostthesameasthoseinthebimetallicPdIrandPdNicatalysts.
CVandCPresultsprovedthatthePd7IrNi12/CcatalystshowedthehighestperformancefortheEORinalkalinemedia,whichcouldbeattributedtotheconcurrentlyfunctionalmechanismduetotheadditionofIr,alongwithNi.
FuelcellperformancetestsshowedthattheuseofthePd7IrNi12/CcatalystastheanodeofanAEMDEFCcouldyieldapeakpowerdensityof49mWcm2in1.
0MKOHsolutioncontaining1.
0Methanolat60C,whichwas122%higherthanthatwithPd/C,44%higherthanthatwithPd2Ni3/Cand69%higherthanthatwithPd7Ir/C;wheninamodest–highFig.
5CPcurvesoftheEORonthePd/C,Pd2Ni3/C,Pd7Ir/CandPd7IrNi12/Ccatalystsin1.
0MKOH+1.
0Methanol(currentdensity:20mAcm2).
Fig.
6Polarizationandpower–densitycurvesoftheAEMDEFCwithdifferentanodecatalysts(Anode:1.
0MKOH+1.
0Methanol).
Fig.
7Polarizationandpower–densitycurvesoftheAEMDEFCwithdifferentanodecatalysts(Anode:5.
0MKOH+3.
0Methanol).
1432|EnergyEnviron.
Sci.
,2011,4,1428–1433ThisjournalisTheRoyalSocietyofChemistry2011concentrationofsolutionat60C,thepeakpowerdensitywas92mWcm2,whichwas58%higherthanthatwithPd/C,15%higherthanthatwithPd2Ni3/C,and28%higherthanthatwithPd7Ir/C.
AcknowledgementsTheworkdescribedinthispaperwasfullysupportedbyagrantfromtheResearchGrantsCounciloftheHongKongSpecialAdministrativeRegion,China(ProjectNo.
623709).
Notesandreferences1E.
AntoliniandE.
R.
Gonzalez,J.
PowerSources,2010,195,3431.
2J.
S.
SpendelowandA.
Wieckowski,Phys.
Chem.
Chem.
Phys.
,2007,9,2654.
3S.
Q.
SongandP.
Tsiakaras,Appl.
Catal.
,B,2006,63,187.
4E.
Antolini,J.
PowerSources,2007,170,1.
5C.
BianchiniandP.
K.
Shen,Chem.
Rev.
,2009,109,4183.
6E.
Antolini,EnergyEnviron.
Sci.
,2009,2,915.
7X.
Fang,L.
Q.
Wang,P.
K.
Shen,G.
F.
CuiandC.
Bianchini,J.
PowerSources,2010,195,1375.
8Z.
Y.
Zhou,Q.
Wang,J.
L.
Lin,N.
TianandS.
G.
Sun,Electrochim.
Acta,2010,55,7995.
9V.
Bambagioni,C.
Bianchini,A.
Marchionni,J.
Filippi,F.
Vizza,J.
Teddy,P.
SerpandM.
Zhiani,J.
PowerSources,2009,190,241.
10C.
Bianchini,V.
Bambagioni,J.
Filippi,A.
Marchionni,F.
Vizza,P.
BertandA.
Tampucci,Electrochem.
Commun.
,2009,11,1077.
11C.
W.
Xu,Z.
Q.
Tian,P.
K.
ShenandS.
P.
Jiang,Electrochim.
Acta,2009,53,2610.
12S.
Y.
Shen,T.
S.
Zhao,J.
B.
XuandY.
S.
Li,J.
PowerSources,2010,195,1001.
13Z.
X.
Liang,T.
S.
Zhao,J.
B.
XuandL.
D.
Zhu,Electrochim.
Acta,2009,54,2203.
14S.
T.
Nguyen,H.
M.
Law,H.
T.
Nguyen,N.
Kristian,S.
Wang,S.
H.
ChanandX.
Wang,Appl.
Catal.
,B,2009,91,507.
15Y.
Wang,T.
S.
Nguyen,X.
W.
LiuandX.
Wang,J.
PowerSources,2010,195,2619.
16Q.
G.
He,W.
Chen,S.
Mukerjee,S.
ChenandF.
Laufek,J.
PowerSources,2009,187,298.
17C.
C.
Qiu,R.
Shang,Y.
F.
Xie,Y.
R.
Bu,C.
Y.
LiandH.
Y.
Ma,Mater.
Chem.
Phys.
,2010,120,323.
18J.
BagchiandS.
K.
Bhattacharya,TransitionMet.
Chem.
,2007,32,47.
19F.
Ksar,L.
Ramos,B.
Keita,L.
Nadjo,P.
BeaunierandH.
Remita,Chem.
Mater.
,2009,21,3677.
20L.
S.
Jou,J.
K.
Chang,T.
J.
TwhangandI.
W.
Sun,J.
Electrochem.
Soc.
,2009,156,D193.
21L.
D.
Zhu,T.
S.
Zhao,J.
B.
XuandZ.
X.
Liang,J.
PowerSources,2009,187,80.
22J.
B.
Xu,T.
S.
Zhao,S.
Y.
ShenandY.
S.
Li,Int.
J.
HydrogenEnergy,2010,35,6490.
23R.
N.
SinghandA.
Singh,Carbon,2009,47,271.
24T.
MaiyalaganandK.
Scott,J.
PowerSources,2010,195,5246.
25V.
Stamenkovic,B.
S.
Moon,K.
J.
Mayerhofer,P.
N.
Ross,N.
Markovic,J.
Rossmeisl,J.
GreeleyandJ.
K.
Norskov,Angew.
Chem.
,Int.
Ed.
,2006,45,2897.
26A.
Kowal,M.
Li,M.
Shao,K.
Sasaki,M.
B.
Vukmirovic,J.
Zhang,N.
S.
Marinkovic,P.
Liu,A.
I.
FrenkelandR.
R.
Adzic,Nat.
Mater.
,2009,8,325.
27S.
J.
Liao,K.
A.
Holmes,H.
TsaprailisandV.
I.
Birss,J.
Am.
Chem.
Soc.
,2006,128,3504.
28P.
Strasser,J.
Comb.
Chem.
,2008,10,216.
29S.
Y.
Shen,T.
S.
ZhaoandJ.
B.
Xu,Electrochim.
Acta,2010,55,9179.
30Y.
S.
Li,T.
S.
ZhaoandZ.
X.
Liang,J.
PowerSources,2009,190,223.
31Y.
S.
Li,T.
S.
ZhaoandW.
W.
Yang,Int.
J.
HydrogenEnergy,2010,35,5656.
32C.
PalacioandA.
Arranz,J.
Phys.
Chem.
B,2000,104,9647.
33Y.
M.
Liang,H.
M.
Zhang,H.
X.
Zhong,X.
B.
Zhu,Z.
Q.
Tian,D.
Y.
XuandB.
L.
Yi,J.
Catal.
,2006,238,468.
34K.
W.
Park,J.
H.
Choi,B.
K.
Kwon,S.
A.
LeeandY.
E.
Sung,J.
Phys.
Chem.
B,2002,106,1869.
ThisjournalisTheRoyalSocietyofChemistry2011EnergyEnviron.
Sci.
,2011,4,1428–1433|1433