电极过程动力学(陈胜利)1

化学学院物理化学专业研究生课程“电极过程动力学〞授课教师：陈胜利

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Office:化学楼1－35授课教材查全性等著：?电极过程动力学导论?〔第三版，科学出版社，2002年〕推荐参考书WrittenbyAllenJ.BardandLarryF.Faulkner,?ElectrochemicalMethods:FundamentalsandApplications?〔SecondEdition,Wiley,2001〕邵元华等译,?电化学方法：原理及应用?〔第二版，化学工业出版社,2005年〕Chapter1INTRODUTIONANDOVERVIEWOFELECTRODEPROCESSESElectrochemistry?Thelaws(principles)andthetechnologiesconcerningtheconversionbetweenchemicalenergyandelectricalenergyInterrelationbetweenchemicalphenomena(chemicalreactions,chemicalchanges,etc.)andelectricphenomena(charge,current,potential,electricfield,etc.)Withahistoryofmorethantwocenturies,electrochemistryhasbeenatypicalexampleofatrulyinterdisciplinary(各学科间的)areaofscienceandtechnology.Itsrootshavebeeninchemistry,physics,materialsandbiologicalscienceanditsapplicationsspreadingfromelectrochemicalanalysisandsynthesistoenvironmentalprotectionandenergyconversionandstorage.Everydaylifeitemssuchasbatteries,theglucose〔葡萄糖〕sensoranddomesticormedicalgassensorsarenowacommodity,whiletheprospectofmassproductionof"green"electricvehicles(Electricvehicles)isnomoreachallengebutaviableoption.Onanindustrialscale,apartfromthenowmaturechlor-alkaliandmetalfinishingandextractionindustries,thereissignificantactivityintheareasofenergyconversionandstoragebymeansoffuelcellsandsolarcellsaswellasintheuseofelectrochemicalmethodsforeffluenttreatment.“Electrochemistryprovidesmanyopportunitiesforsustainabledevelopment.〞ElectrochemicalCellsandReactions

PtPtPtPtH2SO4SolutionH2O2H2O2H+H+H2OH+H2OH+e－e－e－e－Cathode:1/2O2+2H++2e-=H2OAnode:H2=2H++2e-Overallcellreaction:H2+1/2O2=H2OPositiveelectrode:H2O=1/2O2+2H++2e-Negativeelectrode:2H++2e-=H2Overallcellreaction:H2O

=H2+1/2O2

GalvanicCell〔原电池〕VoltaicCellH+H+ThefeaturesofelectrochemicalreactionsTheoverallredoxreactionismadeupoftwohalf-reactionstakingplaceindependentlyattwolocationswhereelectronicconductors(Electrodes)andionicconductors(electrolytes)aremadeincontact;Charge(electronorions)transferbetweentheelectrodesandchemicalspeciesalwaysoccursandacurrentflowsinexternalcircuitbetweentwoelectrodes;Theextentandthedirectionofthereactioncanbealteredbythepotentialsappliedtotheelectrodes;Electrodereactionatelectrode/solutioninterfacesChargetransferplaneFeimilevelLUMOHOMOChargetransferplaneFeimilevelPotentialshiftsnegativelyeOz+eRz-1Fe3++e

Fe2+ForExample:PossibleprocessesinvolvedinanelectrodereactionO'adO'R'adR'O*R*neObRb

Masstransfer

MasstransferPrecedingChemicalreactionsFollowingChemicalreactions

ElectrodeChargetransferAdsorptionDesorptionWhatwillwedealwithinthiscourse?ThekineticsoftheelectrodereactionsofvarioustypeandthefactorsthataffectthesekineticsCurrent—PotentialdependenceThephilosophyinelectrochemicalstudiesSchematicthree-electrodecellusedinelectrochemicalstudiesStandardHydrogenElectrode(SHE)

Pt

CH+=1mol.l-1

H2H2Saturatedcalomelelectrode(SCE)

MetalwireKClsolutionHg2Cl2

HgPtwireStrategiestostudytheelectrodeprocessesPotential-controlledtechniquesCurrent-controlledtechniquesPotentiostatic〔恒电势〕methodsPotentiodynamicmethodsAbriefdescriptionoftheelectricdoublelayeranditseffectsontheelectrodereactionkineticsThedoublelayerisaresultofre-arrangementandorientationofthechargesandthedipolesattheelectrode/electrolyteinterface.Theelectrodeandtheelectrolytebearthesameamountofchargeswithoppositenature:qM=-qS;Thedoublelayerconsistsoftworegions:Compactlayer(alsocalled“innerHelmholtzlayer〞or“sternlayer〞)anddiffuselayer(alsocalled“outerHelmholtzlayer〞);Theeffectivepotentialtodrivetheinterfacialchargetransfermaybesignificantlydifferentfromthatappliedthetheelectrode/solutioninterface:Eeff=Eapp(<1)Thecapacitor〔电容器〕-likenatureoftheelectricdoublelayerRegardlessofthenatureofanelectrodeprocess,thedoublelayeritselfwouldresponsetotheelectrochemicalperturbationsasaseriesofcapacitorsThecapacitancevaluesofthedoublelayerarepotential-dependentMostoftheelectrochemicalmeasurementsaremoreorlessaffectedbythechargingprocessofthedoublelayerCcompactCdiffuseiRsolutionThedoublelayerchargingeffectsinelectrochemicalmeasurement