B. E. Conway

J. O’M. Bockris

The present collection of articles follows the arrangement used in previous volumes. Solutions are discussed first, surfaces and double layers second, electrode kinetics third, and then the applied subjects. The introduction of spectroscopic methods to electrochemistry is well exemplified by NMR studies of ionic solutions, as represented here in the detailed article by E. von Goldammer. Correspondingly, the spectroscopic approach can be applied to surfaces, and B. G. Baker has written an introduction to this topic for electrochemists from the point of view of gas phase measurements. One of the topics which begins to reach a degree of sophistica tion in electrode process chemistry is the adsorption of organic species on electrodes, and this topic is described in our volume by the well-known electrochemist M. W. Breiter. The work has much rele vance to the corresponding electrode kinetics and oxidation of organic materials. Much less sophisticated is the position in the electrochemistry of sulfide minerals, but it has seemed worthwhile to have the present record described by D. F. A. Koch; his chapter demonstrates the value of qualitative electrochemical studies in this field. The Hydrogen Economy is perhaps an example of straw fire in electrochemistry, for its great popularity beginning in 1973 reflects an interest which can hardly grow larger. However, much discussion of the Hydrogen Economy is concerned with its nonelectrochemical v vi Preface aspects and D. P. Gregory gives here the latest from the hydrogen front, with emphasis on the electrochemistry.

Modern Aspects of Electrochemistry

The first model for the distribution of ions near the surface of a metal electrode was devised by Helmholtz in 1874. He envisaged two parallel sheets of charges of opposite sign located one on the metal surface and the other on the solution side, a few nanometers away, exactly as in the case of a parallel plate capacitor. The rigidity of such a model was allowed for by Gouy and Chapman inde pendently, by considering that ions in solution are subject to thermal motion so that their distribution from the metal surface turns out diffuse. Stern recognized that ions in solution do not behave as point charges as in the Gouy-Chapman treatment, and let the center of the ion charges reside at some distance from the metal surface while the distribution was still governed by the Gouy-Chapman view. Finally, in 1947, D. C. Grahame transferred the knowledge of the struc ture of electrolyte solutions into the model of a metal/solution interface, by en visaging different planes of closest approach to the electrode surface depending on whether an ion is solvated or interacts directly with the solid wall. Thus, the Gouy-Chapman-Stern-Grahame model of the so-called electrical double layer was born, a model that is still qualitatively accepted, although theoreti cians have introduced a number of new parameters of which people were not aware 50 years ago.

Scientific Fundamentals and Technological Applications

Electrochemical Supercapacitors

Carol Korzeniewski

Proceedings of the Symposium on the Electrochemical Double Layer

J. O'M. Bockris

In the last decade, the evolution of electrochemistry away from concern with the physical chemistry of solutions to its more fruitful goal in the study of the widespread consequences of the transfer of electric charges across interphases has come to fruition. The turning of technology away from an onward rush, regardless, to progress which takes into account repercussions of techno logical activity on the environment, and the consequent need for a reduction and then termination of the injection of CO into 2 the atmosphere (greenhouse effect), together with a reckoning with air and water pollution in general, ensures a long-term need for advances in a basic knowledge of electrochemical systems, an increased technological use of which seems to arise from the environmental necessities. But a mighty change in attitude needs to spread among electro chemists (indeed, among all surface chemists) concerning the terms and level in which their field is discussed. The treatment of charge transfer reactions has often been made too vaguely, in terms, it seemed, of atom transfer, with the electron-transfer step, the essence of electrochemistry, an implied accompaniment to the transfer of ions across electrical double layers. The treatment has been in terms of classical mechanics, only tenable while inadequate questions were asked concerning the behavior of the electron in the interfacial transfer. No process demands a more exclusively quantal discussion than does electron transfer.

B. E. Conway

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