TOF的计算方法_精品文档.pdf

TOF的计算方法_精品文档.pdf

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SupportinginformationforSynthesisofPtPdBimetalNanocrystalswithControllableShape,CompositionandTheirTunableCatalyticPropertiesXiaoqingHuang,YujingLi,YongjiaLi,HailongZhou,XiangfengDuan,andYuHuang*DepartmentofMaterialsScienceandEngineering,DepartmentofChemistryandBiochemistry,andCaliforniaNanoSystemsInstitute,Univer-sityofCalifornia,LosAngeles,California90095,UnitedStatesEmail:

yhuangseas.ucla.eduExperimentalDetailsChemicals:

Sodiumtetrachloropalladate（Na2PdCl4,99.9%）,Potassiumtetrachloroplatinate（K2PtCl4,99.9%）,Sodiumchloride（NaCl,ACSreagent,99.5%）,Sodiumbromide（NaBr,ACSreagent,99.5%）,Sodiumiodide（NaI,ACSreagent,99.5%）,Poly（vinylpyrrolidone）（PVP,MW55000）andN,N-dimethylformamide（DMF）wereallpurchasedfromSigma-Aldrich.Allthechemicalswereusedasreceivedwithoutfurtherpurification.Thewater（18M/cm）usedinallexperimentswaspreparedbypassingthroughanultrapurepurificationsystem（AquaSolutions）.SynthesisofCubicPtPdNanocrystals:

InatypicalsynthesisofcubicPtPdnanocrystals,sodiumtetrachloropalladate（Na2PdCl4,20mM,ie.0.67mL,1.0mLor1.33mL）,potassiumtetrachloroplatinate（K2PtCl4,20mM,ie.1.33mL,1.0mLor0.67mL）,sodiumiodide（NaI,75.0mg）andpoly（vinylpyrrolidone）（PVP,160.0mg）weremixedtogetherwith10mLN,N-dimethylformamideina22.0-mLvial.Afterthevialhadbeencapped,themixturewasultrasonicatedforaround2minutes.Theresultinghomogeneousmixturewastransferredintoaconventionalovenandheatedat130Cfor5hoursbeforeitwascooledtoroomtemperature.Theresultingcolloidalproductswerecollectedbycentrifugationandwashedseveraltimeswithanethanol-acetonemixture.SynthesisofOctahedralPtPdNanocrystals:

InatypicalsynthesisofoctahedralPtPdnanocrystals,sodiumtetrachloropalladate（Na2PdCl4,20mM,ie.0.67mL,1.0mLor1.33mL）,potassiumtetrachloroplatinate（K2PtCl4,20mM,ie.1.33mL,1.0mLor0.67mL）,sodiumchloride（NaCl,29.3mg）andpoly（vinylpyrrolidone）（PVP,160.0mg）weremixedtogetherwith10mLN,N-dimethylformamideina22.0-mLvial.Afterthevialhadbeencapped,themixturewasultrasonicatedforaround2minutes.Theresultinghomogeneousmixturewastransferredintoaconventionalovenandheatedat130Cfor5hoursbeforeitwascooledtoroomtemperature.Theresultingcolloidalproductswerecollectedbycentrifugationandwashedseveraltimeswithanethanol-acetonemixture.Characterization:

TEMimageswerecarriedoutonaFEICM120transmissionelectronmicroscopeoperatedat120kV.HighresolutionTEMimagesandthehigh-angleannulardark-fieldscanningtransmissionelectronmicroscopy（HAADF-STEM）-energy-dispersiveX-rayspectroscopy（EDS）wasweretakenonaFEITITANtransmissionelectronmicroscopeoperatedat300kV.Thesampleswerepreparedbydroppingethanoldispersionofsamplesontocarbon-coatedcopperTEMgrids（TedPella,Redding,CA）usingpipettesanddriedunderambientcondition.X-raypowderdiffractionpatternswerecollectedonaPanalyticalXPertProX-rayPowderDiffractometerwithCu-Kradiation.Theconcentrationofcatalystswasdeterminedbytheinductivelycoupledplasmaatomicemissionspectroscopy（TJARADIALIRIS1000ICP-AES）.GeneralProcedureforHydrogenationofNitrobenzene:

Inatypicalcatalyticreaction,nitrobenzene（2.0mmol）,PtPdcatalystssuspensioninethanol（0.1mM,1.0mL）andethanol（9.0mL）weremixedtogetherandplacedintoaglasspressurevessel.Inordertoremovetheairfromthereactionsystem,thevesselwaspurgedwithH2beforethecatalyticreaction.Then,thevesselwaspressurizedwith1bar.Duringthecatalyticexperiment,thepressureofH2wasmaintainedconstant.TheintermediatecatalyticproductsproducedatdifferentreactiontimewereanalyzedbyGC-MS.Turn-Over-Frequency（TOF）Calculations（a）Generalconcept1.TOFofthecatalyst=（moleofnitrobenzeneconversion）/（moleofsurfaceatomsofcatalystreactiontime）2.SincebothPdandPthaveaface-centered-cubicstructurewithasimilarlatticeconstant（latticeconstantofPdis0.389nm,latticeconstantofPtis0.392nm）,wecollectivelyusedalatticeconstantof0.39nminthealloyedPtPdnanocrystalsforthesimplicityofcalculation.So,thevolumeofaunitcellinPtPdnanocrystalsis（0.39nm）3=0.059nm3.Eachunitcellcontains4Pt&Pdatoms.3.Anoctahedronwithanedgelengthofahasasurfaceareaof322aandavolumeof323a.Ancubewithanedgelengthofbhasasurfaceareaof62bandavolumeof3b.4.PtPdoctahedronisenclosedby111facet.Eachtwo-dimensionalunitcellonthe111facetscontains0.5Pt&Pdatoms.Theareaofthisunitcellis341268.2=0.031nm2.PtPdnanocubeisenclosedby100facet.Eachtwo-dimensionalunitcellonthe100facetscontains2Pt&Pdatoms.Theareaofthisunitcellis（0.39nm）2=0.15nm2.（b）NumberofPt&PdatomsineachPtPdnanocrystalsNumberofPt&PdatomsineachoctahedralPtPdnanocrystals=（volumeofeachoctahedron/volumeofeachunitcell）at