北京大學(xué)電分析電分析化學(xué)原理、方法和應(yīng)用elec1c課件

FundamentalsofElectroanalyticalChemistry

電分析化學(xué)原理、方法和應(yīng)用

YuanhuaShao（邵元華，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 主要內(nèi)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電化學(xué)基礎(chǔ)，張祖訓(xùn)，汪爾康，200010生命科學(xué)中的電分析化學(xué)，彭圖治，楊麗菊編著,199911*電極過程動力學(xué)導(dǎo)論，查全性，1976(19872ndEdition)12電化學(xué)研究方法，田昭武，198413*電化學(xué)測定方法，騰島昭等著，陳震等譯，199514電分析化學(xué)，蒲國剛，袁倬斌，吳守國編著，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(導(dǎo)言)電分析化學(xué)和電化學(xué)：兩者沒有區(qū)別！基本原理相同，僅研究的側(cè)重點可能不同。電化學(xué)池：

原電池(GalvanicCell)：化學(xué)能電能 電解池(ElectrolyticCell)：電能化學(xué)能一個簡單的電分析化學(xué)實驗：組成：工作(研究)電極(W),參比電極(R)，輔助(對)電極(C),電解質(zhì)溶液，恒電位儀(potentiostat),PC計算機(接口+軟件)。研究重點ElectroanalyticalChemistry

isthebranchofchemistryconcernedwiththeinterrelationofelectricalandchemicaleffects.Alargepartofthisfielddealswiththestudyofchemicalchangescausedbythepassageofanelectriccurrentandtheproductionofelectricalenergybychemicalreactions.Infact,thefieldofelectrochemistryencompassesahugearrayofdifferentphenomena(e.g.,electrophoresisandcorrosion),devices(electrochromicdisplays,electro-analyticalsensors,batteries,andfuelcells),andtechnologies(theelectroplatingofmetalsandthelarge-scaleproductionofaluminumandchlorine).Whilethebasicprinciplesofelectro-chemistrydiscussedinthistextapplytoallofthese,themainemphasishereisontheapplicationofelectrochemicalmethodstothestudyofchemicalsystems.1.2ScopeofElectroanalyticalChemistryVariablesaffectingtherateofanelectrodereaction1.3電化學(xué)的簡史：LuigiGalvani(1737-1798):從1786年開始，進(jìn)行著名的"animal electricity“實驗－解剖青蛙AlessandroVolta(1745-1827):HumphryDavy(1778-1829):MichaelFaraday(1791-1867):Grove: 燃料電池(1839)Lippmann: 1873Helmholtz: 雙電層(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發(fā)展了各種理論，研究方法等R.Marcus: 1950s-1960s,ElectronTransferTheory(NobelPrize Winner,1992)T.Kuwana: 1960s,光譜電化學(xué)Gavach,Korytaetal:1970s開始研究液/液界面電化學(xué)MillerandMurray:1975,化學(xué)修飾電極M.Fleischmann,A.Bewicketal:1970sto1980s,insitu光譜、波譜電化學(xué)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.應(yīng)用領(lǐng)域：1.化學(xué)電源(電池,燃料電池)：2.電解電鍍：3.腐蝕：4.電化學(xué)合成：5.電催化：6.生物電分析化學(xué)：7.電化學(xué)傳感器：Ion-SelectiveElectrodes8.TAS9.單細(xì)胞和單分子測量白鼠腦神經(jīng)遞質(zhì)活體伏安分析示意圖Polarography(極譜)andVoltammetry(伏安法)的區(qū)別？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:兩電極和三電極系統(tǒng)有什么區(qū)別？為什么一般的電化學(xué)研究需用三電極系統(tǒng)？May1,2000;pp.346A-352A(AnalyticalChemistry)VoltammetryRetrospectiveAllenJ.Bard,UniversityofTexas-AustinandCynthiaG.Zoski,UniversityofRhodeIsland電分析化學(xué)的特點：

interdisciplinarynatureandversatility異相反應(yīng)，與表面、界面及相關(guān)的區(qū)域有關(guān)，可控催化。電化學(xué)及電分析化學(xué)的發(fā)展趨勢1，與納米技術(shù)相結(jié)合2，與生物、生命科學(xué)相結(jié)合

信息科學(xué)生命科學(xué)能源科學(xué)環(huán)境科學(xué)材料科學(xué)2.1 導(dǎo)言，原電池和電解池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根據(jù)IUPAC的規(guī)定，左邊的半反應(yīng)是氧化反應(yīng)(anode,陽極)，右邊的半反應(yīng)是還原反應(yīng)(cathode,陰極)Ecell=Eright-EleftPotential:電位，電勢但物理學(xué)，“位”與“勢”的概念是不同的。空間某點的電位，是將單位正電荷從無窮遠(yuǎn)處(或以無任何力作用的無窮遠(yuǎn)的真空為參考點)移到該點所做的功，它具有絕對的意義。電勢則是空間兩點的電位差(或電位降)，如金屬和其離子溶液所形成的電極電勢，實際上是金屬和溶液兩相之間電位差的一種衡量，又是該電極電勢與標(biāo)準(zhǔn)電極電勢差的一種衡量。電化學(xué)池： anode cathode

原電池(GalvanicCell)：化學(xué)能電能 - +電解池(ElectrolyticCell)：電能化學(xué)能+ -一些電化學(xué)池既可以作為原電池，也可以作為電解池，例如；汽車用的Lead-acid電池，在放電時是原電池，反應(yīng)為：anode(-ve): Pb+SO42-

→PbSO4 +2ecathode(+ev): PbO2 +4H+ +SO42-+2e→2H2O+PbSO4在充電時為電解池，上述半反應(yīng)倒過來！Question:為什么Lead-acid電池或其它的電池可以充電？2.2 電池的電動勢和電極電勢界面電勢(絕對電勢及絕對電勢差)內(nèi)電勢(Galvani,),外電勢(Volta,)和表面電勢()外電勢(Volta,):將單位正電荷從無窮遠(yuǎn)處的真空中移到物體近旁距表面約10-4cm處作的功。(是可測的)金屬和電解質(zhì)溶液界面外電勢之差，叫做Volta電勢：=電極-溶液表面電勢()：將單位正電荷從物體表面附近的一點移到物體相內(nèi)所做的電功稱之為表面電勢(涉及到化學(xué)作用，是不可測的)。= + “電位”與“電勢”的區(qū)別！=+=ze=ze=ze+ze+=ze+(電化學(xué)勢)Figure.Aschematicdiagramtoillustratethat,intheinterphaseregion(indicatedbyshading),theregenerallyisnetdipoleorientationandnet,orexcess,chargedensityAnelectrodeislikeagiantcentralionElectrode/electrolyteDoublelayerDoublelayersarecharacteristicofallphaseboundaries1V,1nm,thefieldstrength(gradientofpotential)isenormous-itisoftheorder107V/cm.Theeffectofthisenormousfieldattheelectrode-electrolyteinterfaceis,inasense,theessenceofelectrochemistry!A(a)物質(zhì)相的內(nèi)電勢、外電勢和表面電勢(b)電極與溶液間的內(nèi)電位差和外電位差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電池電動勢和電極電勢電池電動勢：將電位差計接在電池的兩個電極之間而直接測得的電勢值習(xí)慣上稱之為電池的電動勢電極電勢：當(dāng)采用相對電勢法時，系用一定的參比電極與研究電極組成電池，這一電池的電動勢稱為相對于給定參比電極而確定的研究電極電勢。(金屬和溶液相接觸的內(nèi)電位差即為金屬電極和溶液間的電極電勢)所謂“電極/溶液”之間的絕對電勢不但無法直接測量，在處理電極過程動力學(xué)問題時也不需要用到它！在計算電池電動勢時，也完全可以采用相對電極電勢來代替絕對電極電勢！2.3 計算電極電勢(E)：活度or濃度？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,中譯本，p61-71，查全性，電極過程動力學(xué)導(dǎo)論，第二版，第二章)

a=C2.4 電極的分類一般來說，電極可以分為如下四類：(1). A.一個金屬電極與它的水溶液中的離子相接觸,e.g. Cu/Cu2+ E=Eo+RT/(F)lnaMz+半反應(yīng)：Mz+ +ze=M B.一個非金屬它的離子相接觸，e.g.H2/H+或 Cl2/Cl-在一個惰性導(dǎo)電物質(zhì)表面上E=Eo+RT/(F)lnPH21/2/aH+(2)一個金屬電極與一個水溶液中的陰離子相接觸，此陰離子可與金屬電極的離子形成難溶物。例如：Hg/Hg2Cl2/Cl-，thecalomelelectrode(甘汞電極)(3)惰性電極，Pt,Au,C,Hgetc(4)上述不能包括的電極，例如：化學(xué)修飾電極等2.5 參比電極顧名思義，參比電極是給出一個固定的值，其它的電極電勢的測量以此為基礎(chǔ)。一個好的參比電極應(yīng)該不受溫度、時間和通過小電流而變化,應(yīng)遵守Nernst方程！Type1:thehydrogenelectrodeType2:thecalomelelectrodeType3:glasselectrode,ion-selectiveelectrodes各種參比電極的制備和鹽橋的制備(電化學(xué)測定方法，騰島昭等著，陳震等譯，1995。P87-99)ThehydrogenelectrodeThesaturatedcalomelelectrode2.7 電導(dǎo)和淌度(mobility)i=ziuiF(ui是離子淌度子)(i是一種離子的摩爾導(dǎo)電率)=ii=zi2F2Di/RT Nernst-EinsteinrelationDi=kBT/(6r) Stokes-Einsteinrelationti=i/ transportnumber2.8 液接電勢Liquidjunctionpotentialsaretheresultofdifferencecationandanionmobilitiesundertheinfluenceofanelectricfield.Liquidjunctionpotentialcanbeclassifiedintothreetypes:(1)Twosolutionsofthesameelectrolytebutwithdifferentconcentrations(2)Twosulotionsofthesameconcentrationofoneoftheions,buttheotheriondiffers(3)Othercases.Ecell=ENernst+Ej

減小液接電勢的主要方法是應(yīng)用鹽橋。2.9 離子選擇性電極和生物膜離子選擇性電極(Ion-SelectiveElectrodes)是一種能在多種離子存在下，用電位法測量溶液中給定離子活度的分析測量工具。是電化學(xué)傳感器的基礎(chǔ)。E=E0

2.303RT/(ziF)lgaiNikolsky-Eisen