Principles of Electrochemistry Second Edition Jin Koryta Institute of Physiology, Czechoslovak Academy of Sciences, Prague •Win Dvorak Department of Physical Chemistry, Faculty of Science, Charles University, Prague Ladislav Kavan /. Heyrovsky Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, Prague JOHN WILEY & SONS Chichester • New York • Brisbane • Toronto • Singapore Copyright © 1987, 1993 by John Wiley & Sons Ltd. Baffins Lane, Chichester, West Sussex PO19 1UD, England All rights reserved. No part of this book may be reproduced by any means, or transmitted, or translated into a machine language without the written permission of the publisher. Other Wiley Editorial Offices John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, USA Jacaranda Wiley Ltd, G.P.O. Box 859, Brisbane, Queensland 4001, Australia John Wiley & Sons (Canada) Ltd, Worcester Road, Rexdale, Ontario M9W 1L1, Canada John Wiley & Sons (SEA) Pte Ltd, 37 Jalan Pemimpin #05-04, Block B, Union Industrial Building, Singapore 2057 Library of Congress Cataloging-in-Publication Data Koryta, Jifi. Principles of electrochemistry.—2nd ed. / Jin Koryta, Jin Dvorak, Ladislav Kavan. p. cm. Includes bibliographical references and index. ISBN 0 471 93713 4 : ISBN 0 471 93838 6 (pbk) 1. Electrochemistry. I. Dvorak, Jin, II. Kavan, Ladislav. III. Title. QD553.K69 1993 541.37—dc20 92-24345 CIP British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 0 471 93713 4 (cloth) ISBN 0 471 93838 6 (paper) Typeset in Times 10/12 pt by The Universities Press (Belfast) Ltd. Printed and bound in Great Britain by Biddies Ltd, Guildford, Surrey Contents Preface to the First Edition xi Preface to the Second Edition xv Chapter 1 Equilibrium Properties of Electrolytes 1 1.1 Electrolytes: Elementary Concepts 1 1.1.1 Terminology 1 1.1.2 Electroneutrality and mean quantities 3 1.1.3 Non-ideal behaviour of electrolyte solutions 4 1.1.4 The Arrhenius theory of electrolytes 9 1.2 Structure of Solutions 13 1.2.1 Classification of solvents 13 1.2.2 Liquid structure 14 1.2.3 Ionsolvation 15 1.2.4 Ion association 23 1.3 Interionic Interactions 28 1.3.1 The Debye-Huckel limiting law 29 1.3.2 More rigorous Debye-Hiickel treatment of the activity coefficient 34 1.3.3 The osmotic coefficient 38 1.3.4 Advanced theory of activity coefficients of electrolytes 38 1.3.5 Mixtures of strong electrolytes 41 1.3.6 Methods of measuring activity coefficients 44 1.4 Acids and Bases 45 1.4.1 Definitions 45 1.4.2 Solvents and self-ionization 47 1.4.3 Solutions of acids and bases 50 1.4.4 Generalization of the concept of acids and bases 59 1.4.5 Correlation of the properties of electrolytes in various solvents 61 1.4.6 The acidity scale 63 1.4.7 Acid-base indicators 65 1.5 Special Cases of Electrolytic Systems 69 1.5.1 Sparingly soluble electrolytes 69 v VI 1.5.2 Ampholytes 70 1.5.3 Polyelectrolytes 73 Chapter 2 Transport Processes in Electrolyte Systems 79 2.1 Irreversible Processes 79 2.2 Common Properties of the Fluxes of Thermodynamic Quantities 81 2.3 Production of Entropy, the Driving Forces of Transport Phenomena 84 2.4 Conduction of Electricity in Electrolytes 87 2.4.1 Classification of conductors 87 2.4.2 Conductivity of electrolytes 90 2.4.3 Interionic forces and conductivity 93 2.4.4 The Wien and Debye-Falkenhagen effects 98 2.4.5 Conductometry 100 2.4.6 Transport numbers 101 2.5 Diffusion and Migration in Electrolyte Solutions 104 2.5.1 The time dependence of diffusion 105 2.5.2 Simultaneous diffusion and migration 110 2.5.3 The diffusion potential and the liquid junction potential . . . Ill 2.5.4 The diffusion coefficient in electrolyte solutions 115 2.5.5 Methods of measurement of diffusion coefficients 118 2.6 The Mechanism of Ion Transport in Solutions, Solids, Melts, and Polymers 120 2.6.1 Transport in solution 121 2.6.2 Transport in solids 124 2.6.3 Transport in melts 127 2.6.4 Ion transport in polymers 128 2.7 Transport in a flowing liquid 134 2.7.1 Basic concepts 134 2.7.2 The theory of convective diffusion 136 2.7.3 The mass transfer approach to convective diffusion 141 Chapter 3 Equilibria of Charge Transfer in Heterogeneous Electrochemical Systems 144 3.1 Structure and Electrical Properties of Interfacial Regions 144 3.1.1 Classification of electrical potentials at interfaces 145 3.1.2 The Galvani potential difference 148 3.1.3 The Volta potential difference 153 3.1.4 The EMF of galvanic cells 157 3.1.5 The electrode potential 163 3.2 Reversible Electrodes 169 3.2.1 Electrodes of the first kind 170 3.2.2 Electrodes of the second kind 175 Vll 3.2.3 Oxidation-reduction electrodes 177 3.2.4 The additivity of electrode potentials, disproportionation . . . 180 3.2.5 Organic redox electrodes 182 3.2.6 Electrode potentials in non-aqueous media 184 3.2.7 Potentials at the interface of two immiscible electrolyte solutions 188 3.3 Potentiometry 191 3.3.1 The principle of measurement of the EMF 191 3.3.2 Measurement of pH 192 3.3.3 Measurement of activity coefficients 195 3.3.4 Measurement of dissociation constants 195 Chapter 4 The Electrical Double Layer 198 4.1 General Properties 198 4.2 Electrocapillarity 203 4.3 Structure of the Electrical Double Layer 213 4.3.1 Diffuse electrical layer 214 4.3.2 Compact electrical layer 217 4.3.3 Adsorption of electroneutral molecules 224 4.4 Methods of the Electrical Double-layer Study 231 4.5 The Electrical Double Layer at the Electrolyte-Non-metallic Phase Interface 235 4.5.1 Semiconductor-electrolyte interfaces 235 4.5.2 Interfaces between two electrolytes 240 4.5.3 Electrokinetic phenomena 242 Chapter 5 Processes in Heterogeneous Electrochemical Systems . . 245 5.1 Basic Concepts and Definitions 245 5.2 Elementary outline for simple electrode reactions 253 5.2.1 Formal approach 253 5.2.2 The phenomenological theory of the electrode reaction 254 5.3 The Theory of Electron Transfer 266 5.3.1 The elementary step in electron transfer 266 5.3.2 The effect of the electrical double-layer structure on the rate of the electrode reaction 274 5.4 Transport in Electrode Processes 279 5.4.1 Material flux and the rate of electrode processes 279 5.4.2 Analysis of polarization curves (voltammograms) 284 5.4.3 Potential-sweep voltammetry 288 5.4.4 The concentration overpotential 289 5.5 Methods and Materials 290 5.5.1 The ohmic electrical potential difference 291 5.5.2 Transition and steady-state methods 293 Vlll 5.5.3 Periodic methods 301 5.5.4 Coulometry 303 5.5.5 Electrode materials and surface treatment 305 5.5.6 Non-electrochemical methods 328 5.6 Chemical Reactions in Electrode Processes 344 5.6.1 Classification 345 5.6.2 Equilibrium of chemical reactions 346 5.6.3 Chemical volume reactions 347 5.6.4 Surface reactions 350 5.7 Adsorption and Electrode Processes 352 5.7.1 Electrocatalysis 352 5.7.2 Inhibition of electrode processes 361 5.8 Deposition and Oxidation of Metals 368 5.8.1 Deposition of a metal on a foreign substrate 369 5.8.2 Electrocrystallization on an identical metal substrate 372 5.8.3 Anodic oxidation of metals 377 5.8.4 Mixed potentials and corrosion phenomena 381 5.9 Organic Electrochemistry 384 5.10 Photoelectrochemistry 390 5.10.1 Classification of photoelectrochemical phenomena 390 5.10.2 Electrochemical photoemission 392 5.10.3 Homogeneous photoredox reactions and photogalvanic effects 393 5.10.4 Semiconductor photoelectrochemistry and photovoltaic effects 397 5.10.5 Sensitization of semiconductor electrodes 403 5.10.6 Photoelectrochemical solar energy conversion 406 Chapter 6 Membrane Electrochemistry and Bioelectrochemistry . . 410 6.1 Basic Concepts and Definitions 410 6.1.1 Classification of membranes 411 6.1.2 Membrane potentials 411 6.2 Ion-exchanger Membranes 415 6.2.1 Classification of porous membranes 415 6.2.2 The potential of ion-exchanger membranes 417 6.2.3 Transport through a fine-pore membrane 419 6.3 Ion-selective Electrodes 425 6.3.1 Liquid-membrane ion-selective electrodes 425 6.3.2 Ion-selective electrodes with fixed ion-exchanger sites 428 6.3.3 Calibration of ion-selective electrodes 431 6.3.4 Biosensors and other composite systems 431 6.4 Biological Membranes 433 6.4.1 Composition of biological membranes 434 6.4.2 The structure of biological membranes 438 6.4.3 Experimental models of biological membranes 439 6.4.4 Membrane transport 442 6.5 Examples of Biological Membrane Processes 454 IX 6.5.1 Processes in the cells of excitable tissues 454 6.5.2 Membrane principles of bioenergetics 464 Appendix A Recalculation Formulae for Concentrations and Activity Coefficients 473 Appendix В List of Symbols 474 Index 477 Preface to the First Edition Although electrochemistry has become increasingly important in society and in science the proportion of physical chemistry textbooks devoted to electrochemistry has declined both in extent and in quality (with notable exceptions, e.g. W. J. Moore's Physical Chemistry). As recent books dealing with electrochemistry have mainly been ad- dressed to the specialist it has seemed appropriate to prepare a textbook of electrochemistry which assumes a knowledge of basic physical chemistry at the undergraduate level. Thus, the present text will benefit the more advanced undergraduate and postgraduate students and research workers specializing in physical chemistry, biology, materials science and their applications. An attempt has been made to include as much material as possible so that the book becomes a starting point for the study of monographs and original papers. Monographs and reviews (mainly published after 1970) pertaining to individual sections of the book are quoted at the end of each section. Many reviews have appeared in monographic series, namely: Advances in Electrochemistry and Electrochemical Engineering (Eds P. Delahay, H. Gerischer and C. W. Tobias), Wiley-Interscience, New York, published since 1961, abbreviation in References AE. Electroanalytical Chemistry (Ed. A. J. Bard), M. Dekker, New York, published since 1966. Modern Aspects of Electrochemistry (Eds J. O'M. Bockris, В. Е. Conway and coworkers), Butterworths, London, later Plenum Press, New York, published since 1954, abbreviation MAE. Electrochemical compendia include: The Encyclopedia of Electrochemistry (Ed. C. A. Hempel), Reinhold, New York, 1961. Comprehensive Treatise of Electrochemistry (Eds J. O'M. Bockris, В. Е. Conway, E. Yeager and coworkers), 10 volumes, Plenum Press, 1980- 1985, abbreviation CTE. Electrochemistry of Elements (Ed. A. J. Bard), M. Dekker, New York, a multivolume series published since 1973. xi Xll Physical Chemistry. An Advanced Treatise (Eds H. Eyring, D. Henderson and W. Jost), Vol. IXA,B, Electrochemistry, Academic Press, New York, 1970, abbreviation PChAT. Hibbert, D. B. and A. M. James, Dictionary of Electrochemistry, Macmillan, London, 1984. There are several more recent textbooks, namely: Bockris, J. O'M. and A. K. N. Reddy, Modern Electrochemistry, Plenum Press, New York, 1970. Hertz, H. G., Electrochemistry—A Reformulation of Basic Principles, Springer-Verlag, Berlin, 1980. Besson, J., Precis de Thermodynamique et Cinetique Electrochimique, Ellipses, Paris, 1984, and an introductory text. Koryta, J., Ions y Electrodes y and Membranes, 2nd Ed., John Wiley & Sons, Chichester, 1991. Rieger, P. H., Electrochemistry, Prentice-Hall, Englewood Cliffs, N.J., 1987. The more important data compilations are: Conway, В. Е., Electrochemical Data, Elsevier, Amsterdam, 1952. CRC Handbook of Chemistry and Physics (Ed. R. C. Weast), CRC Press, Boca Raton, 1985. CRC Handbook Series in Inorganic Electrochemistry (Eds L. Meites, P. Zuman, E. B. Rupp and A. Narayanan), CRC Press, Boca Raton, a multivolume series published since 1980. CRC Handbook Series in Organic Electrochemistry (Eds L. Meites and P. Zuman), CRC Press, Boca Raton, a multivolume series published since 1977. Horvath, A. L., Handbook of Aqueous Electrolyte Solutions, Physical Properties, Estimation and Correlation Methods, Ellis Horwood, Chiches- ter, 1985. Oxidation-Reduction Potentials in Aqueous Solutions (Eds A. J. Bard, J. Jordan and R. Parsons), Blackwell, Oxford, 1986. Parsons, R., Handbook of Electrochemical Data, Butterworths, London, 1959. Perrin, D. D., Dissociation Constants of Inorganic Acids and Bases in Aqueous Solutions, Butterworths, London, 1969. Standard Potentials in Aqueous Solutions (Eds A. J. Bard, R. Parsons and J. Jordan), M. Dekker, New York, 1985. The present authors, together with the late (Miss) Dr V. Bohackova, published their Electrochemistry, Methuen, London, in 1970. In spite of the favourable attitude of the readers, reviewers and publishers to that book (German, Russian, Polish, and Czech editions have appeared since then) we now consider it out of date and therefore present a text which has been largely rewritten. In particular we have stressed modern electrochemical хш materials (electrolytes, electrodes, non-aqueous electrochemistry in gene- ral), up-to-date charge transfer theory and biological aspects of electro- chemistry. On the other hand, the presentation of electrochemical methods is quite short as the reader has access to excellent monographs on the subject (see page 301). The Czech manuscript has been kindly translated by Dr M. Hyman- Stulikova. We are much indebted to the late Dr A Ryvolova, Mrs M. Kozlova and Mrs D. Tumova for their expert help in preparing the manuscript. Professor E. Budevski, Dr J. Ludvik, Dr L. Novotny and Dr J. Weber have supplied excellent photographs and drawings. Dr K. Janacek, Dr L. Kavan, Dr K. Micka, Dr P. Novak, Dr Z. Samec and Dr J. Weber read individual chapters of the manuscript and made valuable comments and suggestions for improving the book. Dr L. Kavan is the author of the section on non-electrochemical methods (pages 319 to 329). We are also grateful to Professor V. Pokorny, Vice-president of the Czechoslovak Academy of Sciences and chairman of the Editorial Council of the Academy, for his support. Lastly we would like to mention with devotion our teachers, the late Professor J. Heyrovsky and the late Professor R. Brdicka, for the inspiration we received from them for our research and teaching of electrochemistry, and our colleague and friend, the late Dr V. Bohackova, for all her assistance in the past. Prague, March 1986 Jifi Koryta Jin Dvorak [...]...Preface to the Second Edition The new edition of Principles of Electrochemistry has been considerably extended by a number of new sections, particularly dealing with 'electrochemical material science' (ion and electron conducting polymers, chemically modified electrodes ), photoelectrochemistry, stochastic processes, new aspects of ion transfer across biological membranes, biosensors, etc In view of this extension... illustration of the variability of the results obtained by various methods, the values obtained for the Na+ ion 23 from mobility measurements were 2- 4, from the entropy 4, from the compressibility 6- 7, from molar volumes 5, from diffusion 1 and from activity coefficients also 1 For the Cl~ ion, these methods yielded the values (in the same order): 4, 3, 0, — 1, 0, 0, 1 Of the divalent ions, for example, solution... However, as will be seen later, the acidity or basicity of substances appears only on interaction with the medium with which they are in contact References Dunsch, L ., Geschichte der Elektrochemie, Deutscher Verlag fur Grundstoffindustrie, Leipzig, 1985 Ostwald, W ., Die Entwicklung der Elektrochemie in gemeinverstdndlicher Darstellung, Barth, Leipzig, 1910 1.2 1.2.1 Structure of Solutions Classification of. .. dipole moment of water than of nitrobenzene, the ions will be preferentially solvated by water Under these conditions the following values of hydration numbers were obtained: Li+ 6. 5, H + 5. 5, Ag+ 4. 4, Na+ 3. 9, K+ 1. 5, Tl + 1. 0, Rb + 0. 8, Cs + 0. 5, tetraethylammonium ion 0. 0, CIO4-O. 4, NO^ 1.4 and tetraphenylborate anion 0.0 (assumption) 1.2.4 Ion association As already mentioned, the criterion of complete... sum of the hydration numbers of the cation and the anion Similarly, concepts of solvation must be employed in the measurement of equilibrium quantities to explain some anomalies, primarily the salting-out effect Addition of an electrolyte to an aqueous solution of a non-electrolyte results in transfer of part of the water to the hydration sheath of the ion, decreasing the amount of 'free' solvent, and... from the dependence of the standard potential on the temperature for electrodes of the second kind) Otherwise, the heat of solution is the measurable quantity Knowledge of the lattice energy then permits calculation of the heat of hydration For a saturated solution, the heat of solution is equal to the product of the temperature and the entropy of solution, from which the entropy of the salt in the... assume the presence of the structure of ice I with loosely arranged six-membered rings and of structures similar to that of ice III with tightly packed rings Most often, it is assumed that the structure 15 consists of clusters of the ice I type, with various degrees of polymerization, with the maximum of the cluster size distribution in the region of oligomers and with a low concentration of large species... value of the heat of vaporization, entropy of vaporization, boiling point, and dielectric constant of water compared with similar simple substances, such as hydrogen sulphide, hydrogen fluoride, and ammonia Ionic liquids are also not completely randomly arranged but have a structure similar to that of a crystal However, in contrast to crystals, the ionic liquid structure contains far more vacancies, interstitial... solubility of the nonelectrolyte decreases This effect depends, however, on the electrolyte selected In addition, the activity coefficient values (obtained, for example, by measuring the freezing point) can indicate the magnitude of hydration numbers Exchange of the open structure of pure water for the more compact structure of the hydration sheath is the cause of lower compressibility of the electrolyte... dependence of a on c is given in Fig 1.2 For strong electrolytes, the activity of molecules cannot be considered, as no molecules are present, and thus the concept of the dissociation constant loses its meaning However, the experimentally determined values of the dissociation constant are finite and the values of the degree of dissociation differ from unity This is not the result of incomplete dissociation, . Electrochemistry, Plenum Press, New York, 1970. Hertz, H. G ., Electrochemistry A Reformulation of Basic Principles, Springer-Verlag, Berlin, 1980. Besson, J ., . Bard, J. Jordan and R. Parsons ), Blackwell, Oxford, 1986. Parsons, R ., Handbook of Electrochemical Data, Butterworths, London, 1959. Perrin, D. D .,