Modern Electrochemistry 1: Ionics

813 Pages·1998·41.871 MB·English

by  John O’M. Bockris, Amulya K. N. Reddy (auth.)

VOLUME 1
MODERN
ELECTROCHEMISTRY
SECOND EDITION
Ionics
VOLUME 1
MODERN
ELECTROCHEMISTRY
SECOND EDITION
Ionics
John O’M. Bockris
Distinguished Professor of Chemistry
Texas A&M University
College Station, Texas
and
Amulya K. N. Reddy
President
International Energy Initiative
Bangalore, India
KLUWER ACADEMIC PUBLISHERS
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To P. Debye and E. Hückel
PREFACE TO THE FIRST EDITION
This book had its nucleus in some lectures given by one of us (J.O’M.B.) in a course
on electrochemistry to students of energy conversion at the University of Pennsylva-
nia. It was there that he met a number of people trained in chemistry, physics, biology,
metallurgy, and materials science, all of whom wanted to know something about
electrochemistry. The concept of writing a book about electrochemistry which could
be understood by people with very varied backgrounds was thereby engendered. The
lectures were recorded and written up by Dr. Klaus Muller as a 293-page manuscript.
At a later stage, A.K.N.R. joined the effort; it was decided to make a fresh start and to
write a much more comprehensive text.
Of methods for direct energy conversion, the electrochemical one is the most
advanced and seems the most likely to become of considerable practical importance.
Thus, conversion to electrochemically powered transportation systems appears to be
an important step by means of which the difficulties of air pollution and the effects of
an increasing concentration in the atmosphere of carbon dioxide may be met. Corro-
sion is recognized as having an electrochemical basis. The synthesis of nylon now
contains an important electrochemical stage. Some central biological mechanisms
have been shown to take place by means of electrochemical reactions. A number of
American organizations have recently recommended greatly increased activity in
training and research in electrochemistry at universities in the United States. Three
new international journals of fundamental electrochemical research were established
between 1955 and 1965.
In contrast to this, physical chemists in U.S. universities seem—perhaps partly
because of the absence of a modern textbook in English—out of touch with the
revolution in fundamental interfacial electrochemistry which has occurred since 1950.
The fragments of electrochemistry which are taught in many U.S. universities belong
not to the space age of electrochemically powered vehicles, but to the age of thermo-
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viii PREFACE TO THE FIRST EDITION
dynamics and the horseless carriage; they oftenconsist of Nernst’s theory of galvanic
cells (1891) together with the theory of Debye and Hückel (1923).
Electrochemistry at present needs several kinds ofbooks. For example, it needs
a textbook in which the whole field is discussed at a strongtheoretical level. The most
pressing need, however, is for a book whichoutlines the field at a level which can be
understood by people entering it from different disciplines who have no previous
background in the field but who wish to use modern electrochemical concepts and
ideas as a basis for their own work. It is this need which the authors have tried to meet.
The book’s aims determine its priorities. In order, these are:
1. Lucidity. The authors havefound students who understand advanced courses
in quantum mechanics but find difficulty in comprehending a field at whose center
lies the quantum mechanics of electron transitions across interfaces. The difficulty is
associated, perhaps, with the interdisciplinarycharacter of the material: a background
knowledge of physical chemistry is not enough. Material has therefore sometimes been
presented in several ways and occasionally the same explanations are repeated in
different parts of the book. The language has been made informal and highly expla-
natory. It retains, sometimes, the lecture style. In thisrespect, the authors have been
influenced by The Feynman Lectures on Physics.
2. Honesty. The authors have suffered much themselves from books in which
proofs and presentations are not complete. An attempt has been made to include most
of the necessary material. Appendices have been often used for the presentation of
mathematicalderivations which would obtrude too much in the text.
3. Modernity. There developed during the 1950s a great change in emphasis in
electrochemistry away from a subject which dealt largely with solutions to one in
which the treatment at a molecular level of charge transfer across interfaces dominates.
This is the “new electrochemistry,” the essentials of which, at an elementary level, the
authors have tried to present.
4. Sharp variation is standard. The objective of the authors has been to begin each
chapter at a very simple level and to increase the level to one which allows a connecting
up to the standard of the specialized monograph. The standard at which subjects are
presented has been intentionally variable, depending particularly on the degree to
which knowledge of the material appears to be widespread.
5. One theory per phenomenon. The authors intend a teaching book, which acts
as an introduction to graduate studies. They havetried to present, with due admission
of the existing imperfections, a simple version of that model which seemed to them at
the time of writing to reproduce the facts most consistently. They have for the most
partrefrained from presenting the detailed pros and cons of competingmodels in areas
in which the theory is still quite mobile.
In respect to references and further reading: no detailed references to the literature
have been presented, in view of the elementary character of the book’s contents, and
the corresponding fact that it is an introductory book, largely for beginners. In the
PREFACE TO THE FIRST EDITION ix
“further reading” lists, the policy is to cite papers which are classics in the development
of the subject, together with papers of particular interest concerningrecent develop-
ments, and in particular, reviews of the last few years.
It is hoped that this book will not only be useful to those who wish to work with
modern electrochemical ideas in chemistry, physics, biology, materials science, etc.,
but also to those who wish to begin research on electron transfer at interfaces and
associated topics.
The book was written mainly at the Electrochemistry Laboratory in the University
of Pennsylvania, and partly at the Indian Institute of Science in Bangalore. Students
in the Electrochemistry Laboratory at the University of Pennsylvania were kind
enough to give guidance frequently on how they reacted to the clarity of sections
written in various experimental styles and approaches. For the last four years, the
evolving versions of sections of the book have been used as a partial basis for
undergraduate, and some graduate, lectures in electrochemistry in the Chemistry
Department of the University.
The authors’ acknowledgment and thanks must go first to Mr. Ernst Cohn of the
National Aeronautics and Space Administration. Without his frequent stimulation,
including very frank expressions of criticism, the book might well never haveemerged
from the Electrochemistry Laboratory.
Thereafter, thanks must go to Professor B. E. Conway, University of Ottawa, who
gave several weeks of his time to making a detailed review of the material. Plentiful
help in editing chapters and effecting revisions designed by the authors was given by
the following: Chapters IV and V, Dr. H. Wroblowa (Pennsylvania);Chapter VI, Dr.
C. Solomons (Pennsylvania) and Dr. T. Emi (Hokkaido); Chapter VII, Dr. E. Gileadi
(Tel-Aviv); Chapters VIII and IX, Prof. A. Despic (Belgrade), Dr. H. Wroblowa, and
Mr. J. Diggle (Pennsylvania); Chapter X, Mr. J. Diggle; Chapter XI, Dr. D. Cipris
(Pennsylvania). Dr. H. Wroblowa has to be particularly thanked for essential contributions
to the composition of the Appendix on the measurement of Volta potential differences.
Constructive reactions to the text were given by Messers. G. Razumney, B. Rubin,
and G. Stoner of the Electrochemistry Laboratory. Advice was often sought and
accepted from Dr. B. Chandrasekaran (Pennsylvania), Dr. S. Srinivasan (New York),
and Mr. R. Rangarajan (Bangalore).
Comments on late drafts of chapters were made by a number of the authors’
colleagues, particularly Dr. W. McCoy (Office of Saline Water), Chapter II; Prof. R.
M. Fuoss (Yale), Chapter III; Prof. R. Stokes (Armidale), Chapter IV; Dr. R. Parsons
(Bristol), Chapter VII; Prof. A. N. Frumkin (Moscow), Chapter VIII; Dr. H. Wrob-
lowa, Chapter X; Prof. R. Staehle (Ohio State), Chapter XI. One of the authors
(A.K.N.R.) wishes to acknowledge his gratitude to the authorities of the Council of
Scientific and Industrial Research, India, and the Indian Institute of Science, Banga-
lore, India, for various facilities, not the least of which were extended leaves of
absence. He wishes also to thank his wife and children for sacrificing many precious
hours which rightfully belonged to them.
PREFACE
The textbook Modern Electrochemistry by Bockris and Reddy originated in the needs
of students at the Energy Conversion Institute of the University of Pennsylvania in the
late 1960s. People trained in variousdisciplines from mathematics to biology wanted
to understand the new high-energy-density storage batteries and the doubling of the
efficiency of energy conversion offered by fuel cells over heat engines. The task was
to take a group that seemed to be above average in initiative and present electrochem-
istry well enough to meet theirneeds.
The book turned out to be a great success. Its most marked characteristic
was—is—lucidity. The method used was to start off at low level and then move up in
a series of very small steps. Repetition is part of the technique and does not offend,
for the lesson given each time is the same but is taught differently.
The use of the book spread rapidly beyond the confines of energy conversion
groups. It led to the recognition of physical electrochemistry—the electrochemical
disciplineseen from its roots in physics and physical chemistry, and not as a path to
superior chemical analysis. The book outlined electrochemical science for the first
time in a molecular way, paying due heed to thermodynamics as bedrock but keeping
it as background. The success of the effort has been measured not only by the total
sales but by the fact that another reprinting had to be made in 1995, 25 years after the
first one. The average sales rate of the first edition is even now a dozen copies a month!
Given this background, the challenge of writing a revised edition has been a
memorable one. The changes in the state of electrochemical science in the quarter
century of the book’s life have been broad and deep. Techniques such as scanning
tunneling microscopy enable us to see atoms on electrodes. Computers have allowed
a widespread development of molecular dynamics (MD) calculations and changed the
balance between informed guesses and the timely adjustment of parameters in force
laws to enable MD calculations to lead to experimental values. The long-postponed
introduction of commercial electric cars in the United States has been realized and is
xi
xii PREFACE
the beginning of a great step toward a healthier environment. The use of the new
room-temperature molten salts has made it possible to exploit the advantage of
working with pure liquid electrolytes—no solvent—without the rigors of working at
1000 °C.
All the great challenges of electrochemistry at 2000 A.D. do not have to be
addressed in this second edition for this is an undergraduate text, stressing the teaching
of fundamentals with an occasional preview of the advancing frontier.
The basic attributes of the book are unchanged: lucidity comes first. Since the text
is not a graduate text,there is no confusing balancing of the merits of one model against
those of another; the most probable model at the time of writing is described.
Throughout it is recognized that theoretical concepts rise and fall; a theory that lasts
a generation is doing well.
These philosophies have been the source of some of the choices made when
balancingwhat should be retained and what rewritten. The result is quite heterogene-
ous. Chapters 1 and 2 are completely new. The contributions from neutron diffraction
measurements in solutions and those fromother spectroscopic methods have torn away
many of the veils covering knowledge of the first 1–2 layers of solvent around an ion.
Chapter 3 also contains much new material. Debye and Huckel’s famous calculation
is two generations old and it is surely time to move toward new ideas. Chapter 4, on
the other hand, presents much material on transport that is phenomenological—mate-
rial so basic that it must be presented but shows little variationwithtime.
The last chapter, which is on ionic liquids, describes the continuingevolution that
is the result of the development of low-temperature molten salts and the contributions
of computer modeling. The description of models of molten silicates contains much
of the original material in the first edition, for the models described there are those still
used today.
A new feature is the liberal supply of problems for student solution—about 50
per chapter. This idea has been purloined from the excellent physical chemistry
textbook by Peter Atkins (W. H. Freeman). There are exercises, practice in the use of
the chapter’s equations; problems (the chapter’s material related to actual situations);
and finally, a few much more difficult tasks which are called “microresearch prob-
lems,” each one of which may take some hours to solve.
The authors have not hesitated to call on colleagues for help in understanding new
material and in deciding what is vital and what can be left for the literature. The authors
would particularly like to thank John Enderby (University of Bristol) for his review
of Chapter 2; Tony Haymet (University of Sydney) for advice on the weight to be
given to various developments that followed Debye and Hückel’s ground-breaking
work and for tutoring us on computational advances in respect to electrolytic ion pairs.
Michael Lyons (University of Dublin) is to be thanked for allowing the present authors
use of an advanced chapter on transport phenomena in electrolytes written by him.
Austin Angell (ArizonaState University of Tempe) in particular and DouglasInman
PREFACE xiii
(Imperial College) have both contributed by means of criticisms (not always heeded)
in respect to the way to present the material on structure in pure electrolytes.
Manyother electrochemists have helped by replying to written inquiries.
Dr. Maria Gamboa is to be thanked for extensive editorial work, Ms. Diane
Dowdell for her help with information retrieval, and Mrs. Janie Leighman for her
excellence in typing the many drafts.
Finally, the authors wish to thank Ms. Amelia McNamara and Mr. Ken Howell
of Plenum Publishing for their advice, encouragement, and patience.