北京大学电分析电分析化学原理、方法和应用elec1c课件

FundamentalsofElectroanalyticalChemistry

电分析化学原理、方法和应用

YuanhuaShao（邵元华，教授Ph.D.） CollegeofChemistryandMolecularEngineering PekingUniversityOutline:

1.Principles 2.Methods 3.Applications

Part1 Principles1. Introduction 2. ElectrochemicalCell:Thermodynamic PropertiesandElectrodePotentials 3. TheInterfacialRegion 4. FundamentalsofKineticsand MechanismofElectrodeReactions 5. MassTransport 6. KineticsandTransportinElectrode Reactions Part2 Methods 1 ElectrochemicalExperiments 2 HydrodynamicElectrodes 主要内容GeneralBooks:1*A.J.BardandL.R.Faulkner,Electrochemicalmethods,fundamentalsandapplications,Wiley,NewYork,1980(2ndEdition,2001)2*C.M.A.BrettandA.M.O.Brett,Electrochemistry,Principles,Methods,andApplications,Oxford,19933*SouthamptonElectrochemistryGroup,NewInstrumentalMethodsinElectrochemistry,EllisHorwood,Chichester,19854A.M.Bond,ModernpolarographicmethodsinAnalyticalChemistry,Dekker,NewYork,19805J.Koryta,PrinciplesofElectrochemistry,Wiley,19876P.Delahay,NewInstrumentalmethodsinElectrochemistry,19547R.N.Adams,Electrochemistryatsolidelectrodes,19698*J.O'M.BockrisandA.N.Reddy,ModernElectrochemistry,Plenum,NewYork,19709电化学基础，张祖训，汪尔康，200010生命科学中的电分析化学，彭图治，杨丽菊编著,199911*电极过程动力学导论，查全性，1976(19872ndEdition)12电化学研究方法，田昭武，198413*电化学测定方法，腾岛昭等著，陈震等译，199514电分析化学，蒲国刚，袁倬斌，吴守国编著，1993Series1.ElectroanalyticalChemistry,ed.A.J.Bard2.ModernAspectsofElectrochemistry,eds.J.O'M.Bockris,B.E.Conway,etal.,

JournalsNature,Science,JACS,Angew.Chem.IntEditAnal.Chem.,(May1,2000)J.Phys.Chem.B.,J.Electroanal.Chem.,ElectrochimicaActa,J.Electrochem.Society.,Electroanalysis,ElectrochemicalandSolidStateLetters,J.AppliedElectrochemistry,ElectrochemistryCommunications,J.SolidStateElectrochemistryReviews:AccountsofChemicalResearchAnalyticalChemistryAnnualReviewsofPhysicalChemistryChemicalReviewsWebsites:1.1 Introduction(导言)电分析化学和电化学：两者没有区别！基本原理相同，仅研究的侧重点可能不同。电化学池：

原电池(GalvanicCell)：化学能电能 电解池(ElectrolyticCell)：电能化学能一个简单的电分析化学实验：组成：工作(研究)电极(W),参比电极(R)，辅助(对)电极(C),电解质溶液，恒电位仪(potentiostat),PC计算机(接口+软件)。研究重点ElectroanalyticalChemistry

isthebranchofchemistryconcernedwiththeinterrelationofelectricalandchemicaleffects.Alargepartofthisfielddealswiththestudyofchemicalchangescausedbythepassageofanelectriccurrentandtheproductionofelectricalenergybychemicalreactions.Infact,thefieldofelectrochemistryencompassesahugearrayofdifferentphenomena(e.g.,electrophoresisandcorrosion),devices(electrochromicdisplays,electro-analyticalsensors,batteries,andfuelcells),andtechnologies(theelectroplatingofmetalsandthelarge-scaleproductionofaluminumandchlorine).Whilethebasicprinciplesofelectro-chemistrydiscussedinthistextapplytoallofthese,themainemphasishereisontheapplicationofelectrochemicalmethodstothestudyofchemicalsystems.1.2ScopeofElectroanalyticalChemistryVariablesaffectingtherateofanelectrodereaction1.3电化学的简史：LuigiGalvani(1737-1798):从1786年开始，进行著名的"animal electricity“实验－解剖青蛙AlessandroVolta(1745-1827):HumphryDavy(1778-1829):MichaelFaraday(1791-1867):Grove: 燃料电池(1839)Lippmann: 1873Helmholtz: 双电层(1879)F.G.Cottrell: Cottrell公式1902W.Nernst: Nernst公式1904Tafel: Tafel公式1905Gouy,Chapman: 1905Stern:1924Heyrovsky,Shikata: Polarograph1925(1959NobelPrize Winner)1.J.Butler,M.Volmer: Butler-Volmer公式1924-1930P.Delahay,Gerischer,Frumkin,Levich,Bakeretal:1950sto1960s发展了各种理论，研究方法等R.Marcus: 1950s-1960s,ElectronTransferTheory(NobelPrize Winner,1992)T.Kuwana: 1960s,光谱电化学Gavach,Korytaetal:1970s开始研究液/液界面电化学MillerandMurray:1975,化学修饰电极M.Fleischmann,A.Bewicketal:1970sto1980s,insitu光谱、波谱电化学M.Fleischmann,W.Wightmanetal:ultramicroelectrodes1970s-1980sA.J.Bard: SECM,1989Sagivetal: 1980s,self-assembledmembranesP.Hansmaetal:STM-Electrochemistry,1980sLiorZhangorWang:??????(a)Generalprincipleofstudyingasystembyapplicationofanexcitation(orperturbation)andobservationofresponse.(b)Inaspectrophotometricexperiment,theexcitationislightofdifferentwavelengths(),andtheresponseistheabsorbance(A)curve.(c)Inanelectrochemical(potentialstep)experiment,theexcitationistheapplicationofapotentialstep,andtheresponseistheobservedi-tcurve.应用领域：1.化学电源(电池,燃料电池)：2.电解电镀：3.腐蚀：4.电化学合成：5.电催化：6.生物电分析化学：7.电化学传感器：Ion-SelectiveElectrodes8.TAS9.单细胞和单分子测量白鼠脑神经递质活体伏安分析示意图Polarography(极谱)andVoltammetry(伏安法)的区别？polarographyAclassicalelectroanalyticaltechniquediscoveredin1922byJ.Heyrovsky,forwhichhewasawardedtheNobelPrizeforChemistryin1959.Essentially,itislinear-sweepvoltammetryusingadropping-mercuryelectrodeforworkingelectrodeandalargemercurypoolascounterelectrode.voltammetryAnelectrochemicalmeasuringtechniqueusedforelectrochemicalanalysisorforthedeterminationofthekineticsandmechanismofelectrodereactions."Voltammetry"isafamilyoftechniqueswiththecommoncharacteristicsthatthepotentialoftheworkingelectrodeiscontrolled(typicallywithapotentiostat)andthecurrentflowingthroughtheelectrodeismeasured.Inoneofthemostcommonapplicationsofthetechnique,thepotentialisscannedlinearlyintime;thisiscalledthe"linear-sweepvoltammetry,""LSV,"or"LV.""Cyclicvoltammetry(CV)"isalinear-sweepvoltammetrywiththescancontinuedinthereversedirectionattheendofthefirstscan,thiscyclecanberepeatedanumberoftimes.Figure1.Basicvoltammetry.(a)Apparatusforvoltammetrywithatwo-electrodecell,appropriateforuseinsolutionsoflowresistanceandmicroelectrodes.(b)Apparatusforvoltammetrywithathree-electrodecell.Inpracticeapotentiostatthatautomaticallycontrolsthepotentialoftheworkingelectrodewithrespecttoareferenceelectrodeisused.Question:两电极和三电极系统有什么区别？为什么一般的电化学研究需用三电极系统？May1,2000;pp.346A-352A(AnalyticalChemistry)VoltammetryRetrospectiveAllenJ.Bard,UniversityofTexas-AustinandCynthiaG.Zoski,UniversityofRhodeIsland电分析化学的特点：

interdisciplinarynatureandversatility异相反应，与表面、界面及相关的区域有关，可控催化。电化学及电分析化学的发展趋势1，与纳米技术相结合2，与生物、生命科学相结合

信息科学生命科学能源科学环境科学材料科学2.1 导言，原电池和电解池1.Whyisitthathalf-reactionsinelectrochemicalcellsproceedspontaneouslyinonedirectionandfurnishcurrent?2.Whatistheeffectofthesaltbridge?3.Whatistheeffectofionmigration?4.Whatisabsoluteandrelativepotentialdifferences?Zn/Zn2+(aq),Cu2+(aq)/Cu Hg/Hg2Cl2/Cl-(aq),Zn2+(aq)/ZnAg/AgCl/TBACl(aq)/TBATPB(o)//LiCl(aq)/AgCl/Ag根据IUPAC的规定，左边的半反应是氧化反应(anode,阳极)，右边的半反应是还原反应(cathode,阴极)Ecell=Eright-EleftPotential:电位，电势但物理学，“位”与“势”的概念是不同的。空间某点的电位，是将单位正电荷从无穷远处(或以无任何力作用的无穷远的真空为参考点)移到该点所做的功，它具有绝对的意义。电势则是空间两点的电位差(或电位降)，如金属和其离子溶液所形成的电极电势，实际上是金属和溶液两相之间电位差的一种衡量，又是该电极电势与标准电极电势差的一种衡量。电化学池： anode cathode

原电池(GalvanicCell)：化学能电能 - +电解池(ElectrolyticCell)：电能化学能+ -一些电化学池既可以作为原电池，也可以作为电解池，例如；汽车用的Lead-acid电池，在放电时是原电池，反应为：anode(-ve): Pb+SO42-

→PbSO4 +2ecathode(+ev): PbO2 +4H+ +SO42-+2e→2H2O+PbSO4在充电时为电解池，上述半反应倒过来！Question:为什么Lead-acid电池或其它的电池可以充电？2.2 电池的电动势和电极电势界面电势(绝对电势及绝对电势差)内电势(Galvani,),外电势(Volta,)和表面电势()外电势(Volta,):将单位正电荷从无穷远处的真空中移到物体近旁距表面约10-4cm处作的功。(是可测的)金属和电解质溶液界面外电势之差，叫做Volta电势：=电极-溶液表面电势()：将单位正电荷从物体表面附近的一点移到物体相内所做的电功称之为表面电势(涉及到化学作用，是不可测的)。= + “电位”与“电势”的区别！=+=ze=ze=ze+ze+=ze+(电化学势)Figure.Aschematicdiagramtoillustratethat,intheinterphaseregion(indicatedbyshading),theregenerallyisnetdipoleorientationandnet,orexcess,chargedensityAnelectrodeislikeagiantcentralionElectrode/electrolyteDoublelayerDoublelayersarecharacteristicofallphaseboundaries1V,1nm,thefieldstrength(gradientofpotential)isenormous-itisoftheorder107V/cm.Theeffectofthisenormousfieldattheelectrode-electrolyteinterfaceis,inasense,theessenceofelectrochemistry!A(a)物质相的内电势、外电势和表面电势(b)电极与溶液间的内电位差和外电位差Tomeasurethepotentialdifferenceacrossametal-solutionelectrifiedinterface(seeexplodedview),oneterminalofthepotential-measuringinstrumentisconnectedtothemetalelectrode.Whatistobedonewiththesecondterminal?Allonecanmeasure,inpractice,isthepotentialdifferenceacrossasystemofinterfaces,orcell,notthepotentialdifferenceacrossoneelectrode-electrolyteinterface.TheabsolutepotentialDifferenceacrossasingleelectrifiedinterfacecannotbemeasured!Itisnotnecessarytoknowexactvalueofitbutthedifferenceofabsolutepotentialdifferenceisimportantforelectrochemists!J.O'M.BockrisandA.N.Reddy,ModernElectrochemistry,Plenum,NewYork,1970,p623电池电动势和电极电势电池电动势：将电位差计接在电池的两个电极之间而直接测得的电势值习惯上称之为电池的电动势电极电势：当采用相对电势法时，系用一定的参比电极与研究电极组成电池，这一电池的电动势称为相对于给定参比电极而确定的研究电极电势。(金属和溶液相接触的内电位差即为金属电极和溶液间的电极电势)所谓“电极/溶液”之间的绝对电势不但无法直接测量，在处理电极过程动力学问题时也不需要用到它！在计算电池电动势时，也完全可以采用相对电极电势来代替绝对电极电势！2.3 计算电极电势(E)：活度or浓度？eq=eqo+RT/(zF)lnaMz+=E=Eo+RT/(zF)lnaMz+Nernst公式(方程)O+ze=RE=Eo+RT/(zF)lnaO/aR(A.J.BardandL.R.Faulkner,Electrochemicalmethods,1980,中译本，p61-71，查全性，电极过程动力学导论，第二版，第二章)

a=C2.4 电极的分类一般来说，电极可以分为如下四类：(1). A.一个金属电极与它的水溶液中的离子相接触,e.g. Cu/Cu2+ E=Eo+RT/(F)lnaMz+半反应：Mz+ +ze=M B.一个非金属它的离子相接触，e.g.H2/H+或 Cl2/Cl-在一个惰性导电物质表面上E=Eo+RT/(F)lnPH21/2/aH+(2)一个金属电极与一个水溶液中的阴离子相接触，此阴离子可与金属电极的离子形成难溶物。例如：Hg/Hg2Cl2/Cl-，thecalomelelectrode(甘汞电极)(3)惰性电极，Pt,Au,C,Hgetc(4)上述不能包括的电极，例如：化学修饰电极等2.5 参比电极顾名思义，参比电极是给出一个固定的值，其它的电极电势的测量以此为基础。一个好的参比电极应该不受温度、时间和通过小电流而变化,应遵守Nernst方程！Type1:thehydrogenelectrodeType2:thecalomelelectrodeType3:glasselectrode,ion-selectiveelectrodes各种参比电极的制备和盐桥的制备(电化学测定方法，腾岛昭等著，陈震等译，1995。P87-99)ThehydrogenelectrodeThesaturatedcalomelelectrode2.7 电导和淌度(mobility)i=ziuiF(ui是离子淌度子)(i是一种离子的摩尔导电率)=ii=zi2F2Di/RT Nernst-EinsteinrelationDi=kBT/(6r) Stokes-Einsteinrelationti=i/ transportnumber2.8 液接电势Liquidjunctionpotentialsaretheresultofdifferencecationandanionmobilitiesundertheinfluenceofanelectricfield.Liquidjunctionpotentialcanbeclassifiedintothreetypes:(1)Twosolutionsofthesameelectrolytebutwithdifferentconcentrations(2)Twosulotionsofthesameconcentrationofoneoftheions,buttheotheriondiffers(3)Othercases.Ecell=ENernst+Ej

减小液接电势的主要方法是应用盐桥。2.9 离子选择性电极和生物膜离子选择性电极(Ion-SelectiveElectrodes)是一种能在多种离子存在下，用电位法测量溶液中给定离子活度的分析测量工具。是电化学传感器的基础。E=E0

2.303RT/(ziF)lgaiNikolsky-Eisen