ELSEVIER Journal of Electrnanalytical Chemistry 422 (1997) 201-204

Book reviews

Novel Trends in Electroorganic Synthesis, S. Torii (Ed.), Kodansha, Tokyo, 1995, a ~ + xxxix pp., price ¥ 15000

This book contains summaries of the above 140 papers presented orally and as posters at two symposia, "The Second International Symposium on Electroorganic Syn- thesis" and "Novel Aspects of Electrogenerated Active Species and Their Reactions", held sequentially in South- ern Japan during September 1994.

Each contribution is only two to four pages long and, for full details of the chemistry, the reader will usually need to consult the journal literature (in general, papers contain the necessary references). On the contrary, the book is an excellent and up-to-date snapshot of organic electrochemistry and its applications. Almost all the world's leading research groups were represented at these confer- ences, and the subject matter for the lectures was well chosen. Hence, the book gives a rapid entry into the concepts and practice of modem organic electrosynthesis and describes recent progress in approaches to topics as diverse as the functionalisation of organic molecules, se- lective fluorination, stereoselectivity, chiral synthesis, the synthesis of pharmaceutical intermediates, electrogenerated bases, mediated electrode reactions, organometallic chem- istry, organo Si, S and P chemistry and bioelectrosynthesis. This book will be a very valuable source of information to all those academic and industrial groups involved in elec- trosynthesis.

Derek Pletcher

Electrochromism-- Fundamentals and Applications, P.M.S. Monk, R.J. Mortimer and D.R. Ross,::,nsky, VCH, Weinheim, 1995, xxiii + 216 pp., DM ! 68.00

Electrochromism is defined in this book as the phe- nomenon of colour change exhibited by some redox species on oxidation or reduction. It is the basis of many smart tricks used by magicians and popular chemistry lecturers to entertain their audiences. This book is similarly enter- mining, with many examples of redox colour changes and proposed electrochemical display devices based on electro- chemical cells which produce colour changes in the elec-

trodes or the electrolyte. Such devices have been in the patent files for decades, but improvements in other tech- nologies have generally pushed electrochromics out of first place in the fierce competition for the large volume appli- cations such as calculators, watches, and portable com- puter screens which require fast switching. Nevertheless, electrochromic rear-view mirrors are a commercial product and electrochromics may yet find more niche markets. The possibility of large markets in smart windows and slow- switching, large-area devices is a point which is rather understated in this book despite intensive research and development by the world's major glass manufacturers.

The essential principles of operation are described ac- cording to the rudiments of equilibrium and dynamic electrochemistry. Here the qualitative explanations are cor- rect, but the mathematical equations seem unfamiliar be- cause of the use of unusual sign conventions and symbols. Also, this section omits some essential theory of the thermodynamics of solids which are not adequately de- scribed by the Nemst equation as simplified in terms of concentrations, rather than activities, of the redox species. However, the essential message that mass transport con- trols the switching speed and a tabulation of diffusion coefficients allows the reader to calculate the expected performance. To conclude the first part of the book, some possible construction schemes are given with many exam- ples from the literature which illustrate a wide choice of solid electrolytes and methods of preparing electrode mate- rials in thin film form.

The central section of the book categorises countless electrochromic materials into "Inorganic Systems" (metal oxides, phthalocyanine compounds and Prussian blue) and "Organic Systems" (bipyridilium systems, electroactive conducting polymers and "other organic electrochromes"). The entertainment value now falls sharply, as would that of a magician filling the show with endless variations of the same trick. The enormous number of referenced exam- ples makes us realise that almost everything is elec- trochromic, and that the mere observation of an electro- chemically-generated colour change no longer gives justifi- cation to publish. Most of the reports are of qualitative visual observations so that it is difficult to see an order of merit in performance or a set of criteria by which a material should be regarded as outstanding. However, as an indexed catalogue of previous work in the subject, this

202 Book reciews

is a useful reference source for anyone embarking on novel research in the area.

In the short final section, named "Elaborations", in the French style, we find "polyelectrochromic'" systems capa- ble of covering the red-green-blue spectrum with about as many colours as there are oxidation states. Photoelec- trochromism and electrochromic printing are described, including an archaic fax machine and a few patents which have not gone a long way from the drawing board. It is anybody's guess whether any of these systems, based on electrochromic materials earlier in the book, will ever make an impact in the market place. That will depend on the real inventors who can think of viable new applications first then look for the right materials. And, of course, the entrepreneurs who can find the start-up money, to whom I can recommend this book as essential reading.

John Owen

Modena Aspects of Electiwchemisoy, No. 29, Edited by J.O'M. Bockris, B.E. Conway and Ralph E. White, Plenum Press, New York, 1996, xi + 490 pp, $110, ISBN 0-306-45 ! 62-X

This is a large volume although it contains the usual five chapters.

Chapter l by D.B. Sepa discusses the energies of activation of electrode reaction. In 1948 M I. Temkin published a simple and beautifully dear analysis of the problem of the energy of activation of an electrode reac- tion (ref. 27). His conclusions were as follows.

(l) That the only precise quantity which can be mea- sured is that calculated from the temperature coefficient of the current density at constant overpotential, i.e. with the reference electrode having the same reaction as the work- ing electrode, but at equilibrium and at the same tempera- ture.

(2) That this activation energy is precisely that which can be calculated from a theoretical model.

(3) An activation energy obtained from the temperature coefficient of the current at constant electrode potential requires assumptions about the temperature dependences of the reference electrode which appear equally in a theo- retical calculation in a way which makes the comparison equivalent to that using the constant overpotential condi- tion.

This paper must be one of the most widely misunder- stood in electrochemical kinetics. For many this could be because they have never read the original. Dr. Sepa goes so far as to say "'the Temkin-Agar approach is . . . inadequate" (page 50). The coupling with Agar is in fact misleading because he did not make the principal point made by Temkin.

I should perhaps risk being described as a Stalinist if I say that the present chapter is excessively formalistic with

its elaborate and unnecessary nomenclature. It is fortunate that the author is not a member of a IUPAC Commission. This formalistic approach leads him to the curious result that the 'barrierless' condition is represented by a point on the Tafel line where neither the current nor the overpoten- tial can increase (page 27). It is this lack of physical insight which makes this chapter unhelpful.

Chapter 2 by C.G. Vayenas, M.M. Jaksic, S.I. Bebelis and S.G. Neophytides devotes 140 pages to a review of the Electrochemical Activation of Catalytic Reactions which the authors call the non-faradaic electrochemical modifica- tion of catalytic activity or NEMCA. It is not clear why a faradaic effect would be expected since the effect occurs as a result of the electrolytic production of a promoting species which then migrates from the solid electrolyte support onto the supported catalyst. This subject has been widely reviewed by the principal authors and in fact pages 70 to 100 will be recognised by any readers of ref. 4. This section includes the erroneous claim that work function changes can be measured from the potential difference of a galvanic cell. This rests on the argument (page 90) that the outer potential of a catalyst particle remains unchanged as charge is supplied to it because all the charge will be located at the interface with the support. Conventional electrochemical reactions are covered in seven pages which are based cn a recent paper in Nature (ref. 8) by the present authors.

Chapter 3 by I-H. Pionski concerns the Effect of Sur- face Structure and Adsorption Phenomena on the Active Dissolution of Iron in Acid Media. This is a comprehen- sive survey on the work done by classical (i.e. non-molec- ular level) techniques. The problems of irreproducibility are emphasised and the necd for statistical analysis pointed out. It is evident that this problem is largely due to the lack of detailed control of the surface structure and composi- tion. This is obviously the next major step to be taken in the fundamental understanding of such an important reac- tion. The present review provides a clear summary of the problems which need to be solved. An even greater step is the use of the knowledge then gained, to the practical application in corrosion.

Chapter 4 by S.G. Roscoe covers Electrochemical In- vestigations of the Interfacial Behaviour of Proteins. The emphasis is on the practical problems of the adsorption of proteins in surfaces which are present in the food industry and in medical environments. A variety of electrochemical and non-electrochemical techniques giving information about adsorbed layers of organic compounds, amino acids and proteins is summarised br:zfly. It is surprising that the work of Hill et al. at Oxford ,s not included, nor is Niki's use of electroreflectance to obtain the redox potential of adsorbed cytochrome-c. Nevertheless, the complexity of the adsorption behaviour is emphasised. There is no doubt that the problems of surface fouling by biological products are of great importance and this chapter is welcome in drawing attention to them.