厦大物理化学讲义-物理化学(双语)第六讲(阅读版)new

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1、ElectrochemicalThermodynamicsΔG=−zFE,Nernstequation,μiChemicalCellsSolid/Solid，Solid/Liquid，Liquid-Liquidjunction(contact)potentialMembranepotentialConcentrationCellsEnergyLevelsVacuumE=0LevelEmptyStatesFermiFilledLevelEnergyStatesMoreAtomsManyAtomsBulkAnAtomMetalEnricoFermi（1901－1954）FermiLevelF

2、ermireceivedtheNobelPrizein1938for"hisdiscoveryofnewradioactiveelementsproducedbyneutronirradiation,andforthediscoveryofnuclearreactionsbroughtaboutbyslowneutrons."FermiLevelthetopofthecollectionofelectronenergylevelsatabsolutezerotemperatureE=0(vacuumlevel)CBE(Fermilevel)FEnergyVBMetal1Metal2Fer

3、miEnergy:minimumenergytoremoveelectronfrommetal----(workfunction---workofescapingelectron)TwoMetalsinContact------------++++++++++–+electronflow–+leadstochargeseparation–+–+–+contactpotentialdifferenceFermilevelthesamethroughoutsampleElectrochemicalEquilibriumandFermiLevelTheFermiLevelisEMz+defin

4、edasthehighestLUMOoccupiedorbitalinthevalencebandat0K,sothattherearemanyEfErHOMOstatesavailabletoacceptelectrons,iftheMcaseisforametal.Solid/LiquidChargeTransferRateControlledbyApplyingPotentialEMz+EMz+EMz+eEfErEfErEreEfMMMAtmorenegativeAtopen-circuitAtmorepositivepotentialpotentialpotentialElect

5、rochemicalDoubleLayerofSolid/LiquidandLiquid/LiquidInterfaces−+−OHP−+−−+−PotentialMetal−+−+−Electrolyte−+−0x2xα+β+−−−−++−+−−+PotentialElectrolyte−Electrolyte−+++0xLiquid/liquidjunctionpotential(diffusionpotential)InducedbydifferenceofionicdiffusespeedH+Ag+H+Cl+Δφl1/l2HClHClAgNOHNO33a2

6、idjunctionpotentialbydifferentconcentrationofasinglebinarysaltsolution:z+-(z+-z-)t+RT(ai)1ΔΦl=lnzz+-F(ai)2forasingleelectrolyteofI-Ivalence:RT(a)i1=(t−t)ln+−F(a)i2SaltBridgeARoleofSaltBridgeSaltbridgeΔΦl(1)ΔΦl(2)saturatedsolution(2)solution(1)KClCl-Cl-K+K+junctionpotentialdecreasestoabout1mV!(KNO

7、NHNO)3,43QCKCl>>C1,C2RTC1KCl'Δφl(1)=(tK+−tCl−)lnFC桥KClRTC桥KClΔφl(2)=(tK+−tCl−)lnFC2KCl'Δφl=Δφl(1)+Δφl(2)C1KCl'=(t+−t−)lnKClC'2KClMembranePotentialSemi-permeableMembraneelectrolyte(α)electrolyte(β)M+(α)M+(β)μ+(α)=μ+(β)M