1、 Fundamentals of Electroanalytical Chemistry 电分析化学原理、方法和应用电分析化学原理、方法和应用 Yuanhua Shao（邵元华，教授（邵元华，教授 Ph.D.）College of Chemistry and Molecular Engineering Peking UniversityOutline:1.Principles2.Methods3.ApplicationsPart 1 Principles1.Introduction2.Electrochemical Cell:Thermodynamic Properties and Elect
2、rode Potentials3.The Interfacial Region4.Fundamentals of Kinetics and Mechanism of Electrode Reactions5.Mass Transport6.Kinetics and Transport in Electrode ReactionsPart 2Methods1Electrochemical Experiments2Hydrodynamic Electrodes主要内容主要内容Part 2Methods3Cyclic Voltammetry and Linear SweepTechniques4St
3、ep and Pulse Techniques5Impedance Methods6Non-Electrochemical Probes of Electrodesand Electrode ProcessesPart 3Applications1Potentiometric Sensors2Amperometric and Voltammetric Sensors3Electrochemistry in Industry4Corrosion5Bioelectrochemistry主要内容主要内容General Books:1*A.J.Bard and L.R.Faulkner,Electro
4、chemical methods,fundamentals and applications,Wiley,New York,1980(2nd Edition,2001)2*C.M.A.Brett and A.M.O.Brett,Electrochemistry,Principles,Methods,and Applications,Oxford,19933*Southampton Electrochemistry Group,New Instrumental Methods in Electrochemistry,Ellis Horwood,Chichester,19854 A.M.Bond,
5、Modern polarographic methods in Analytical Chemistry,Dekker,New York,19805 J.Koryta,Principles of Electrochemistry,Wiley,19876 P.Delahay,New Instrumental methods in Electrochemistry,19547 R.N.Adams,Electrochemistry at solid electrodes,19698*J.OM.Bockris and A.N.Reddy,Modern Electrochemistry,Plenum,N
6、ew York,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(1987 2nd Edition)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.Electroanalytical Chemistry,ed.A.J.Bard2.Modern Aspects of Electrochemistry,eds.J.OM.Bockris,B.E.Conway,et al.,JournalsN
7、ature,Science,JACS,Angew.Chem.Int EditAnal.Chem.,(May 1,2000)J.Phys.Chem.B.,J.Electroanal.Chem.,Electrochimica Acta,J.Electrochem.Society.,Electroanalysis,Electrochemical and Solid State Letters,J.Applied Electrochemistry,Electrochemistry Communications,J.Solid State ElectrochemistryReviews:Accounts
8、 of Chemical ResearchAnalytical ChemistryAnnual Reviews of Physical ChemistryChemical ReviewsWebsites:http:/electrochem.cwru.edu/estir/Chapter One(第一章第一章)Introduction(导言导言)1.1Introduction1.2Scope of Electroanalytical Chemistry1.3Brief History1.4Examples1.1 Introduction(导言导言)电分析化学和电化学：电分析化学和电化学：两者没有区
9、别！基本原理两者没有区别！基本原理相同，仅研究的侧重点可能不同。相同，仅研究的侧重点可能不同。电化学池：电化学池：原电池(Galvanic Cell)：化学能 电能电解池(Electrolytic Cell)：电能 化学能一个简单的电分析化学实验：一个简单的电分析化学实验：组成：工作组成：工作(研究研究)电极电极(W),参比电极参比电极(R)，辅助辅助(对对)电极电极(C),电解质溶液，恒电位仪电解质溶液，恒电位仪(potentiostat),PC计算机计算机(接口接口+软件软件)。研究重点研究重点Electroanalytical Chemistry is the branch of che
10、mistry concerned with the interrelation of electrical and chemical effects.A large part of this field deals with the study of chemical changes caused by the passage of an electric current and the production of electrical energy by chemicalreactions.In fact,the field of electrochemistry encompassesa
11、huge array of different phenomena(e.g.,electrophoresisand corrosion),devices(electrochromic displays,electro-analytical sensors,batteries,and fuel cells),and technologies(the electroplating of metals and the large-scale production of aluminum and chlorine).While the basic principles of electro-chemi
12、stry discussed in this text apply to all of these,the main emphasis here is on the application of electrochemical methods to the study of chemical systems.1.2 Scope of Electroanalytical ChemistryScientists make electrochemical measurements on chemical systems for a variety of reasons.They may be int
13、erested in obtaining thermodynamic data about a reaction.They may want to generate an unstable intermediate such as a radical ion and study its rate of decay or its spectroscopic properties.They may seek to analyze a solution for trace amounts of metal ions or organic species.In these examples,elect
14、ro-chemical methods are employed as tools in the study of chemical systems in just the way that spectroscopic methods are frequently applied.There are also investigations in which the electrochemical properties of the systems themselves are of primary interest,for example,in the design of a new powe
15、r source or for the electrosynthesis of some product.Many electrochemical methods have been devised.Their application requires an understanding of the fundamental principles of electrode reactions and the electrical properties of electrode-solution interfaces.Variables affecting the rate of an elect
16、rode reaction1.3 电化学的简史：电化学的简史：Luigi Galvani(1737-1798):从1786年开始，进行著名的animal electricity“实验解剖青蛙Alessandro Volta(1745-1827):Humphry Davy(1778-1829):Michael Faraday(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,Chap
17、man:1905Stern:1924Heyrovsky,Shikata:Polarograph 1925(1959 Nobel PrizeWinner)1.J.Butler,M.Volmer:Butler-Volmer 公式1924-1930P.Delahay,Gerischer,Frumkin,Levich,Baker et al:1950s to 1960s 发展了各种理论，研究方法等R.Marcus:1950s-1960s,Electron Transfer Theory(Nobel Prize Winner,1992)T.Kuwana:1960s,光谱电化学Gavach,Koryta
18、et al:1970s 开始研究液/液界面电化学Miller and Murray:1975,化学修饰电极M.Fleischmann,A.Bewick et al:1970s to 1980s,in situ 光谱、波谱电化学M.Fleischmann,W.Wightman et al:ultramicroelectrodes 1970s-1980sA.J.Bard:SECM,1989Sagiv et al:1980s,self-assembled membranesP.Hansma et al:STM-Electrochemistry,1980sLi or Zhang or Wang:?研究
19、方法：研究方法：稳态和暂态技术：稳态和暂态技术：光谱、波谱技术：光谱、波谱技术：表面技术：表面技术：SPM(Scanning Probe Microscopy)(a)General principle of studying a system by application of an excitation(or perturbation)and observation of response.(b)In a spectrophotometric experiment,the excitation is light of different wavelengths(),and the respo
20、nse is the absorbance(A)curve.(c)In an electrochemical(potential step)experiment,the excitation is the application of a potential step,and the response is the observed i-t curve.应用领域：应用领域：1.化学电源化学电源(电池电池,燃料电池燃料电池)：2.电解电镀：电解电镀：3.腐蚀：腐蚀：4.电化学合成：电化学合成：5.电催化：电催化：6.生物电分析化学：生物电分析化学：7.电化学传感器：电化学传感器：Ion-Sele
21、ctive Electrodes8.TAS9.单细胞和单分子测量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白鼠脑神经递质活体伏安分析示意图Polarography(极谱极谱)and Voltammetry(伏安法伏安法)的区别？的区别？polarographyA classical electroanalytical technique discovered in 1922 by J.Heyrovsky,for which he was awarded the Nobel Prize for Chemistry in 1959.Essentially,it is linear-swee
22、p voltammetry using a dropping-mercury electrode for working electrode and a large mercury pool as counter electrode.voltammetryAn electrochemical measuring technique used for electrochemical analysis or for the determination of the kinetics and mechanism of electrode reactions.Voltammetry is a fami
23、ly of techniques with the common characteristics that the potential of the working electrode is controlled(typically with a potentiostat)and the current flowing through the electrode is measured.In one of the most common applications of the technique,the potential is scanned linearly in time;this is
24、 called the linear-sweep voltammetry,LSV,or LV.Cyclic voltammetry(CV)is a linear-sweep voltammetry with the scan continued in the reverse direction at the end of the first scan,this cycle can be repeated a number of times.Figure 1.Basic voltammetry.(a)Apparatus for voltammetry with a two-electrode c
25、ell,appropriate for use in solutions of low resistance and microelectrodes.(b)Apparatus for voltammetry with a three-electrode cell.In practice a potentiostat that automatically controls the potential of the working electrode with respect to a reference electrode is used.Question:两电极和三电极系统有什么区别？为什么一
26、般的电化学研究需用三电极系统？May 1,2000;pp.346 A-352 A(Analytical Chemistry)Voltammetry RetrospectiveAllen J.Bard,University of Texas-Austin and Cynthia G.Zoski,University of Rhode IslandThree-dimensional voltammetry.Representation of the three-dimensional I-t-E surface for a Nernstian reaction.The typical steady
27、-state voltammogram represents a cut parallel to the I-E plane.(b)A cut representing a linear potential sweep across this surface.(Adapted from Ref.6.)电分析化学的特点：电分析化学的特点：interdisciplinary nature and versatility异相反应异相反应，与表面、界面及相关的，与表面、界面及相关的区域有关，区域有关，可控催化。可控催化。电化学及电分析化学的发展趋势电化学及电分析化学的发展趋势1，与纳米技术相结合与纳米
28、技术相结合2，与生物、生命科学相结合与生物、生命科学相结合 信息科学信息科学生命科学生命科学能源科学能源科学环境科学环境科学材料科学材料科学Chapter Two(第二章第二章)Electrochemical Cells:Thermodynamic Properties and Electrode Potentials2.1Introduction,Galvanic and electrolytic cells2.2The cell potential of an electrochemical cell2.3Calculation of cell potential:activities o
29、r concentrations?2.4Electrode classification2.5Reference electrodes2.6The movement of ions in solution:diffusion and migration2.7Conductivity and mobility2.8Liquid junction potentials2.9Ion-Selective Electrodes and Biomembranes2.1导言，原电池和电解池导言，原电池和电解池1.Why is it that half-reactions in electrochemical
30、 cells proceed spontaneously in one direction and furnish current?2.What is the effect of the salt bridge?3.What is the effect of ion migration?4.What is absolute and relative potential differences?Zn/Zn2+(aq),Cu2+(aq)/CuHg/Hg2Cl2/Cl-(aq),Zn2+(aq)/ZnAg/AgCl/TBACl(aq)/TBATPB(o)/LiCl(aq)/AgCl/Ag根据IUPA
31、C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，电位，电势电势但物理学，但物理学，“位位”与与“势势”的概念是不同的。空间某点的概念是不同的。空间某点的电位，是将单位正电荷从无穷远处的电位，是将单位正电荷从无穷远处(或以无任何或以无任何力作用的无穷远的真空为参考点力作用的无穷远的真空为参考点)移到该点所做的移到该点所做的功，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(或电位降或电位降)，如金属和其离子溶液所形成的电极电势，如金属和其离子
32、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。该电极电势与标准电极电势差的一种衡量。电化学池：电化学池：anode cathode 原电池原电池(Galvanic Cell)：化学能：化学能 电能电能 -+电解池电解池(Electrolytic Cell)：电能：电能 化学能化学能 +-一些电化学池既可以作为原电池，也可以作为电解池，一些电化学池既可以作为原电池，也可以作为电解池，例如；汽车用的例如；汽车用的Lead-acid电池，在放电时是原电池，电池，在放电时是原电池，反应为：反应
33、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！在充电时为电解池，上述半反应倒过来！Question:为什么为什么Lead-acid电池或其它的电池电池或其它的电池可以充电？可以充电？2.2 电池的电动势和电极电势电池的电动势和电极电势界面电势界面电势(绝对电势及绝对电势差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
34、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)。=+“电位电位”与与“电势电势”的区别！的区别！=+=ze=ze=ze+ze+=ze+(电化学势)Figure.A schematic diagram to illustrate that,in theinterphase region(indicated by shading),there generallyis net dipole orientation and net,or excess,charge density
35、An electrode islike a giant central ionElectrode/electrolyteDouble layerDouble layers are characteristic of all phase boundaries1V,1nm,the field strength(gradient of potential)is enormous-it is ofthe order 107 V/cm.The effect of this enormous field at the electrode-electrolyte interface is,in a sens
36、e,the essence of electrochemistry!A(a)物质相的内电物质相的内电势、外电、外电势和表面电势和表面电势(b)电极与溶液间的内电位差和外电位差电极与溶液间的内电位差和外电位差To measure the potential difference across a metal-solution electrified interface(see exploded view),one terminal of the potential-measuring instrument is connected to the metal electrode.What is t
37、o be done with the second terminal?All one can measure,in practice,is the potential difference acrossa system of interfaces,or cell,not the potential difference across one electrode-electrolyte interface.The absolute potential Difference across a singleelectrified interface cannot be measured!It is
38、not necessaryto know exact value of it but the difference of absolute potential difference isimportant for electrochemists!J.OM.Bockris and A.N.Reddy,Modern Electrochemistry,Plenum,New York,1970,p623电池电动势和电极电势电池电动势和电极电势电池电动势电池电动势：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
39、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 计算电极电势计算电极电势(E)：活度活度 or 浓度？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.Bard and L.R.Faulkner,Electrochemical m
40、ethods,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 电极的分类电极的分类一般来说，电极可以分为如下四类：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：半反应：Mz+ze=MB.一个非金属它的离子相接触，一个非金属它的离子相接触，e.g.H2/H+或或Cl2/Cl-在一个惰性导电物质表面上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，一
41、个金属电极与一个水溶液中的阴离子相接触，此阴离子此阴离子可与金属电极的离子形成难溶物。例如：可与金属电极的离子形成难溶物。例如：Hg/Hg2Cl2/Cl-，the calomel electrode(甘汞电极甘汞电极)(3)惰性电极，惰性电极，Pt,Au,C,Hg etc(4)上述不能包括的电极，例如：化学修饰电极等上述不能包括的电极，例如：化学修饰电极等2.5 参比电极参比电极顾名思义，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
42、小电流而变化过小电流而变化,应遵守应遵守Nernst 方程！方程！Type 1:the hydrogen electrodeType 2:the calomel electrodeType 3:glass electrode,ion-selective electrodes各种参比电极的制备和盐桥的制备各种参比电极的制备和盐桥的制备(电化学测定方法，电化学测定方法，腾岛腾岛 昭昭 等著，等著，陈震等译，陈震等译，1995。P87-99)The hydrogen electrodeThe saturated calomel electrode2.7 电导和淌度电导和淌度(mobility)i=z
43、iuiF (ui是离子淌度子)(i 是一种离子的摩尔导电率)=ii=zi2F2Di/RT Nernst-Einstein relation Di=kBT/(6r)Stokes-Einstein relationti=i/transport number2.8 液接电势液接电势Liquid junction potentials are the result of difference cation and anionmobilities under the influence of an electric field.Liquid junction potential can be class
44、ified into three types:(1)Two solutions of the same electrolyte but with different concentrations(2)Two sulotions of the same concentration of one of the ions,but the other ion differs(3)Other cases.Ecell=ENernst+Ej减小液接电势的主要方法是应用盐桥。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和生物膜离子选择性电极离子选择性电极(Ion-Select
45、ive Electrodes)是一种能在多种离子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。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。是电化学传感器的基础。E=E0 2.303RT/(ziF)lgaiNikolsky-Eisenman 方程方程E=K 2.303RT/(ziF)lgai+Kijpot aiz/z作业：作业：1.第一、二章后的习题(A.J.Bard and L.R.Faulkner,Electrochemical methods,fundamentals and applications,Wiley,New York,
46、1980,2001)2.第一章后的习题(电分析化学，蒲国刚，袁倬斌，吴守国编著,1993)作业：1.Devise electrochemical cells in which the following reactions could be made to occur.If liquid junctions are necessary,note them in the cell schematic appropriately,but neglect their effects.(a)H2O H+OH-(b)2H2+O2 H2O(c)2PbSO4+2 H2O PbO2+Pb+4H+2SO42-(
47、d)2Ce3+2 H+BQ 2Ce4+H2Q(aqueous,where BQ is p-benzoquinone and H2Q is p-hydroquinone)(e)Ag+I-AgI(aqueous)(f)Fe3+Fe(CN)64-Fe2+Fe(CN)63-(aqueous)(g)Cu2+Pb Pb2+Cu(aqueous)What half-reactions take place at the electrode in each cell?What is the standard cell potential in each case?Which electrode is negative?Would the cell operate electrolytically or galvanically in carrying out a net reaction from left to right?Be sure your decisions accord with chemical intuition.2.Obtain the dissociation constant of water from the parameters of the cell constructed forreaction(a)in problem 1(T=298K).
