電動勢與熱動力學(xué)燃料電池

電動勢與熱動力學(xué)燃料電池第一頁，共十八頁，編輯于2023年，星期一Reversibility1)ChemicalReversibilityPtis0.222VmorenegativethanAgShortedExternalbatterychemicallyreversible:Reversingthecellcurrentmerelyreversesthecellreaction.Nonewreactionsappear,thusthecellistermed;chemicallyirreversible:differentelectrodereactionsaswellasadifferentnetprocessuponcurrentreversal;第二頁，共十八頁，編輯于2023年，星期一ReversibilityThermodynamicallyreversible:whenaninfinitesimalreversalinadrivingforcecausesittoreversedirectionInelectrochemistryIfasystemfollowstheNernstequationoranequationderivedfromit,theelectrodereactionisoftensaidtobethermodynamicallyorelectrochemicallyreversible(ornernstian).第三頁，共十八頁，編輯于2023年，星期一FreeEnergyandCellemf第四頁，共十八頁，編輯于2023年，星期一ReductionPotentialsTheprimaryreference,chosenbyconvention,isthenormalhydrogenelectrode(NHE),alsocalledthestandardhydrogenelectrode(SHE):第五頁，共十八頁，編輯于2023年，星期一emfandConcentration第六頁，共十八頁，編輯于2023年，星期一ReferenceElectrodes第七頁，共十八頁，編輯于2023年，星期一第八頁，共十八頁，編輯于2023年，星期一ImpedanceSpectroscopy(Or,howasinusoidallyvaryingvoltageisused

toprobemultipleelectricalpropertiesofmaterials)第九頁，共十八頁，編輯于2023年，星期一IntroductionISmeasurestheresistanceofacircuittoanappliedvoltageZ(t)=E(t)/I(t),Z()=E()/I()WhenEisappliedasasinusoidalfunctioninalinearsystem,Iresponsecanberepresentedbyasumofsinusoidalfuctionswithphaseshifts.Ifanequivalentcircuitforthesystembeingprobedcanbeconstructed,thentheresistanceorcapacitancevaluesforeachcircuitelementcanbebackedoutfromZ.Especiallyinelectrochemicalimpendancespectroscopy(EIS),thethevoltageprobesignalissmall(1-10mV)sothecurrentresponseispseudolinear(sidebenefit:itdoesn’tperturbthesampleverymuch)ABardandLFaulkner,ElectrochemicalMethods:FundamentalsandApplications(2000)/G2/Appnotes/Reference/eistheory/theory/EIS_Theory.htm第十頁，共十八頁，編輯于2023年，星期一Background–ImpedanceandCircuitElementsE(t)=E0cos(t),=2fI(t)=I0cos(t-)Or,ifonewritesincomplexnotation:E(t)=E0exp(it)I(t)=I0exp(it-i)Z(t)=Z0exp(i)=Z0(cos+isin)E/Iresponseforaresistor(=0)E/Iresponseforacapacitor(=-90)E/Iresponseforaninductor(=90)/G2/Appnotes/Reference/eistheory/theory/EIS_Theory.htmhttp://www.bath.ac.uk/~chsacf/solartron/circp/html/acrci.htm第十一頁，共十八頁，編輯于2023年，星期一

=-jXc=jXlhttp://www.bath.ac.uk/~chsacf/solartron/circp/html/acrci.htmRFormorecomplexcircuits,useKirchoff’srules第十二頁，共十八頁，編輯于2023年，星期一PlottingImpedance

ACole-Cole(orNyquist)plotoftherealandimaginarycomponentsofZ

foracircuitcontainingacapacitorandresistorinparallel(realworld

example:achargedlayerataninterface).=1/=1/RCNamedafterKSColeandRHCole,JChemPhys

9,341(1941)第十三頁，共十八頁，編輯于2023年，星期一PlottingImpedanceABodeplotofacircuitcontainingacapacitorandresistorinparallel.log|Z|andvs.logareplotted,showingexplicitlytheimpactof

impedance./G2/Appnotes/Reference/eistheory/theory/EIS_Theory.htm第十四頁，共十八頁，編輯于2023年，星期一CircuitElementsfromElectrochemistryElectrolyteresistanceDoublelayercapacitance(~30F/cm2foraqueoussystems)PolarizationresistanceChargetransferresistanceCoatingcapacitance

Constantphaseelement(afudgefactor)Virtualinductor(adsorption?)And…lAWE,RE,CER=l/A/G2/Appnotes/Reference/eistheory/theory/EIS_Theory.htm第十五頁，共十八頁，編輯于2023年，星期一Diffusion(akaWarburgImpedance)Warburgimpedance=diffusionofchemicalspeciestoalargeplanarelectrodeInfinitediffusionlayerthicknessDiffusionlayerthicknessAlso,intheWarburgregion,=45o/resources/eis/diffusion.htm第十六頁，共十八頁，編輯于2023年，星期一EquivalentCircuitModelforElectrochemicalCells

MixedKinetic+DiffusionmodelCole-ColeplotBodeplot/G2/Appnotes/Reference/eistheory/theory/EIS_Theory.htm第十七頁，共十八頁，編輯于2023年，星期一SomeApplicationsofISDeterminecorrosionratesofmaterials*MeasurecapacitanceandresistanceofSAMstoascertainthicknessandpackingqualityProbelinearityofelectrical/electrochemicalreactionsCharacterizeelectricalactivityacrossinterfacestodeterminecarrierconcentration,etc.Determinediffusionrateofcounterionsinconductingpolymer/carbonnanotubecomposit