电极过程动力学(陈胜利).ppt

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Tel 68754693Email slchen 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 Chapter1 INTRODUTIONANDOVERVIEWOFELECTRODEPROCESSES Electrochemistry 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 Pt Pt Pt Pt H2SO4Solution H2 O2 H2 O2 H H H2O H H2O H e e e e Cathode 1 2O2 2H 2e H2OAnode H2 2H 2e Overallcellreaction H2 1 2O2 H2O Positiveelectrode H2O 1 2O2 2H 2e Negativeelectrode 2H 2e H2Overallcellreaction H2O H2 1 2O2 GalvanicCell 原电池 VoltaicCell H H Thefeaturesofelectrochemicalreactions Theoverallredoxreactionismadeupoftwohalf reactionstakingplaceindependentlyattwolocationswhereelectronicconductors Electrodes andionicconductors electrolytes aremadeincontact Charge electronorions transferbetweentheelectrodesandchemicalspeciesalwaysoccursandacurrentflowsinexternalcircuitbetweentwoelectrodes Theextentandthedirectionofthereactioncanbealteredbythepotentialsappliedtotheelectrodes Electrodereactionatelectrode solutioninterfaces Chargetransferplane Feimilevel LUMO HOMO Chargetransferplane Feimilevel Potentialshiftsnegatively e ForExample Possibleprocessesinvolvedinanelectrodereaction O ad O R ad R O R ne Ob Rb Masstransfer Masstransfer PrecedingChemicalreactions FollowingChemicalreactions Electrode Chargetransfer Adsorption Desorption Whatwillwedealwithinthiscourse ThekineticsoftheelectrodereactionsofvarioustypeandthefactorsthataffectthesekineticsCurrent Potentialdependence Thephilosophyinelectrochemicalstudies Schematicthree electrodecellusedinelectrochemicalstudies StandardHydrogenElectrode SHE Pt CH 1mol l 1 H2 H2 Saturatedcalomelelectrode SCE Metalwire KClsolution Hg2Cl2 Hg Ptwire Strategiestostudytheelectrodeprocesses Potential controlledtechniques Current controlledtechniques Potentiostatic 恒电势 methods Potentiodynamicmethods Abriefdescriptionoftheelectricdoublelayeranditseffectsontheelectrodereactionkinetics Thedoublelayerisaresultofre arrangementandorientationofthechargesandthedipolesattheelectrode electrolyteinterface Theelectrodeandtheelectrolytebearthesameamountofchargeswithoppositenature qM qS Thedoublelayerconsistsoftworegions Compactlayer alsocalled innerHelmholtzlayer or sternlayer anddiffuselayer alsocalled outerHelmholtzlayer Theeffectivepotentialtodrivetheinterfacialchargetransfermaybesignificantlydifferentfromthatappliedthetheelectrode solutioninterface Eeff Eapp 1 Thecapacitor 电容器 likenatureoftheelectricdoublelayer Regardlessofthenatureofanelectrodeprocess thedoublelayeritselfwouldresponsetotheelectrochemicalperturbationsasaseriesofcapacitorsThecapacitancevaluesofthedoublelayerarepotential dependentMostoftheelectrochemicalmeasurementsaremoreorlessaffectedbythechargingprocessofthedoublelayer Thedoublelayerchargingeffectsinelectrochemicalmeasurements E RsCdi