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Electrochemical and electrocatalytic reactions from carbon dioxide
Ektrochimica Acta,Vol.39,No. 6,pp.853-854, 1994 ELscvicr6+ckttaLtd. Ptinted inGmt Btitia 0013~4666/94 $6.00 + 0.00
Pergamoa
BOOK REVIEWS ELECTROCHEMISTRY. PRINCIPLES, APPLICATIONS
METHODS
AND
A. BRETTand ANA MARIA OLIVE~RABRMT Oxford Science Publications, 1993,427 pp., E25.
CHRISTOPHER M.
follows a chapter on cyclic voltammetry and one on pulse and step techniques. Again the mathematics is restrained so that the principal equations are placed in context but the flow of the text is not brought to a complete halt. Finally the methods section is concluded by chapters on ac impedance and non-electrochemical techniques for the characterisation of electrode surfaces. To my mind, the balance is slightly out here, with all the in situ and ex situ techniques given only equal space as, say, at impedance or cyclic voltammetry. As a consequence each technique makes only a fleeting appearance and the opportunity to demonstrate how the growing knowledge of the atomic and molecular detail of the structure of the electrode surface is changing our conceptions and abilities in electrochemical science is missed. Applications, the final section of the book, covers a range of topics with chapters on potentiometric sensors, amperometric sensors, industrial electrochemistry, corrosion and bioelectrochemistry. These provide some indication of electrochemistry in its wider context but are not as authoritative or up to date as some of the earlier sections of the book. These are followed by a set of appendices covering the Laplace transform, digital simulation and such like. A comprehensive index is provided but no problems to assist the hard pressed lecturer or to challenge the reader to test their understanding. My main reservation is that there are a number of places where the text is unclear and in some cases incorrect. For example, saying that the space charge region at a semiconductor electrolyte junction arises because of difficulties of electron movement in the semiconductor is to confuse kinetics and thermodynamics and is not helpful to the novice reader. Nevertheless my overall impression is of a good book with an up to date, topical, coverage of electrochemistry. This is one of the better undergraduate texts currently available covering the subject from thermodynamic and solution concepts to electrode kinetics and modem aspects of electrochemistry.
This substantial textbook is divided, as its title suggests, into three sections starting with an introduction to the principles of electrochemistry and then going on to discuss methods and applications. The book is written for undergraduates and assumes no prior knowledge of electrochemistry. The first third of the work, dealing with principles, covers the thermodynamics of electrochemical cells, diffusion and migration of ions, and the conductivity of electrolyte solutions. A notable exception in this section is any reference to, or discussion of, the Debye-Huckel treatment of ionic activity. Thus the concept of the ion atmosphere is not properly described, although it is referred to later in the book. However, the distribution of potential, and ions, at the electrod+electrolyte interface is well described along with a brief discussion of semiconductor/electrolyte junctions. This is followed by chapters on the kinetics of electron transfer reactions, mass transport processes and the effects of combined electrode kinetics and mass transport in electrochemistry. These are generally well presented with about the right amount of mathematical rigour to enable the reader to gather the thrust of the arguments without becoming enmeshed in wall-to-wall mathematics. The material in this section of the book, if covered in full, would provide a good grounding in basic electrochemistry. The middle section of the book, dealing with the methods of electrochemistry, covers much of the ground one would expect. The first chapter contains practical information on the preparation of electrode surfaces, design of electrochemical instrumentation, choice of supporting electrolytes and other such matters. As an introduction it is welcome but the serious experimentalist will need to go to the references at the end before reaching for an electrochemical cell. The next three chapters concern themselves with techniques, starting with hydrodynamic electrodes. Included here we find the rotating disc electrode, of course, but also descriptions of the dropping mercury electrode, as well as wall-jet and channel electrode geometries. Then
ELECTROCHEMICAL AND ELECTROCATALYTIC REACTIONS OF CARBON DIOXIDE Edited by B. P.
SULLIVAN,
K. KRIST
and H. E. GUARD
Elsevier Publishers, Amsterdam, 1993; ISBN O-444-88316-9,ca. E130.
This is, in many ways, a timely book. The electro-reduction of CO,, which is an all but inexhaustible source of carbon, to useful chemical feedstocks has considerable long-term attractions, but the exploratory work that has been carried out over the last 20 years has revealed the immense difli-
cult& that beset the control of multi-step electrochemical processes. It is also important to emphasise that such difficulties are not simply scientific; there are alternatives to the electro-reduction of CO,, the most significant being the direct reduction of CO, by H,. At high temperatures, the
853
854
Book Reviews
equilibrium CO + H,O = CO, + H, lies strongly to the left, and if excess hydrogen is used, chemical reduction to methanol or, with Fischer-Tropsch catalysts, to higher hydrocarbons is possible. Direct electro-reduction of CO, must, then, be competitive with the chemical reduction of CO, by electrolvticallv generated hydrogen, and this book fies&ts a progre& report by a number of North American chemists who have been involved in various aspects of CO, reduction and complexation. The book is, in fact, in two parts, the first of which is primarily concerned with the coordination chemistry of CO, and its reactions with low-valent transitionmetal complexes, and the second is an account of some aspects of the direct electrochemical reduction of CO, at metal and semiconducting electrodes, The coordination chemistry of CO, is well covered, and the two possible routes for CO, uptake, by either direct coordination through mono- or di-hapto ligation or by insertion reactions to yield carboxylato, carbamato or carbonato products, are clearly described and related to the many pathways for transition-metal catalysed CO, reduction that are now known to exist. In this regard, the central chapter in the first section of the book is undoubtedly the fifth, by Keene and Sullivan, which, although covering some of the ground also found in earlier chapters, effectively summa&es the electrocatalytic cycles that have been developed by Ishida, Lehn, Eisenberg and others. For those new to the field, or seeking a good brief introduction, this chapter is ideal. The second half of the book is devoted to three accounts of attempts that have been made to reduce CO, directly at electrode surfaces. The first account, by Frese, is in reality a lengthy report on work carried out in his own group. The report is helpful in that it summa&s a very large amount of data, but the overriding impression left is of how much more will need to be done before the surface chemistry of CO, reduction can be said to be fully understood. Nevertheless, there is much here to stimulate further work and ideas; most valuable without any doubt would be the stimulation of techniques for improved surface characterisation under the highly dynamic conditions operating in the working cells.
Complementary to this chapter is an account by Sammells and Cook of their own recent work on high surfacearea electrodes for CO, reduction. The primary interest of this group has been the reduction of CO, to methane and ethene, particularly on copper electrodes, and this chapter was the only one in the book to address the fundamental problems of engineering the high current density devices that will be needed if the technology is ever to become competitive. Two examples of such technology are given: the use of Na8on electrolytes to fabricate “zero-gap” cells for CO, reduction to CO, CH, and C, hydrocarbons, and the use of perovskite-based catalysts of the form La,_,Sr,CuOs~ to reduce CO, to methanol and higher alcohols. The mechanistic discussion Drovidcd at the end of this chapter is again highly thought-provoking, and an open invitation to devise techniques capable of detecting the many intermediates postulated. Finally, there is an excellent review by Lewis and Shrcve of the photoreduction of CO, both by homogeneous photocatalysis and by illuminated semiconductors. This chapter summarises well the state of knowledge of photocatalysed CO, reduction, and the authors have done a good job in making sense of a literature that is extraordinarily full of contradiction. Any electrochemist hoping to make headway in this area will find this very penetrating account of real value. Taken as a whole, the book is not a comprehensive account; indeed, in so rapidly moving a field it would be impossible to provide such an account, though a more thorough discussion of the immense Japanese effort in the arca could have been provided. The book has clearly been overly long in gestation; a number of articles have 1988 or 1989 as the latest date for references, and this undoubtedly detracts from their timeliness. There is also a considerable amount of repetition in the chapters; editorship has apparently been with a very light hand, as shown by the fact that different chapters have different typefaces. In a book this expensive it is hard to see the justi8cation for not resetting the typescript. The cost of the book certainly places it out of the realms of the private buyer, but it is an indispensable t&e mecum for those interested in CO, chemistry, and is unlikely to be superseded for some time in its specialist niche. A. HAMNETT
Pergamoa
BOOK REVIEWS ELECTROCHEMISTRY. PRINCIPLES, APPLICATIONS
METHODS
AND
A. BRETTand ANA MARIA OLIVE~RABRMT Oxford Science Publications, 1993,427 pp., E25.
CHRISTOPHER M.
follows a chapter on cyclic voltammetry and one on pulse and step techniques. Again the mathematics is restrained so that the principal equations are placed in context but the flow of the text is not brought to a complete halt. Finally the methods section is concluded by chapters on ac impedance and non-electrochemical techniques for the characterisation of electrode surfaces. To my mind, the balance is slightly out here, with all the in situ and ex situ techniques given only equal space as, say, at impedance or cyclic voltammetry. As a consequence each technique makes only a fleeting appearance and the opportunity to demonstrate how the growing knowledge of the atomic and molecular detail of the structure of the electrode surface is changing our conceptions and abilities in electrochemical science is missed. Applications, the final section of the book, covers a range of topics with chapters on potentiometric sensors, amperometric sensors, industrial electrochemistry, corrosion and bioelectrochemistry. These provide some indication of electrochemistry in its wider context but are not as authoritative or up to date as some of the earlier sections of the book. These are followed by a set of appendices covering the Laplace transform, digital simulation and such like. A comprehensive index is provided but no problems to assist the hard pressed lecturer or to challenge the reader to test their understanding. My main reservation is that there are a number of places where the text is unclear and in some cases incorrect. For example, saying that the space charge region at a semiconductor electrolyte junction arises because of difficulties of electron movement in the semiconductor is to confuse kinetics and thermodynamics and is not helpful to the novice reader. Nevertheless my overall impression is of a good book with an up to date, topical, coverage of electrochemistry. This is one of the better undergraduate texts currently available covering the subject from thermodynamic and solution concepts to electrode kinetics and modem aspects of electrochemistry.
This substantial textbook is divided, as its title suggests, into three sections starting with an introduction to the principles of electrochemistry and then going on to discuss methods and applications. The book is written for undergraduates and assumes no prior knowledge of electrochemistry. The first third of the work, dealing with principles, covers the thermodynamics of electrochemical cells, diffusion and migration of ions, and the conductivity of electrolyte solutions. A notable exception in this section is any reference to, or discussion of, the Debye-Huckel treatment of ionic activity. Thus the concept of the ion atmosphere is not properly described, although it is referred to later in the book. However, the distribution of potential, and ions, at the electrod+electrolyte interface is well described along with a brief discussion of semiconductor/electrolyte junctions. This is followed by chapters on the kinetics of electron transfer reactions, mass transport processes and the effects of combined electrode kinetics and mass transport in electrochemistry. These are generally well presented with about the right amount of mathematical rigour to enable the reader to gather the thrust of the arguments without becoming enmeshed in wall-to-wall mathematics. The material in this section of the book, if covered in full, would provide a good grounding in basic electrochemistry. The middle section of the book, dealing with the methods of electrochemistry, covers much of the ground one would expect. The first chapter contains practical information on the preparation of electrode surfaces, design of electrochemical instrumentation, choice of supporting electrolytes and other such matters. As an introduction it is welcome but the serious experimentalist will need to go to the references at the end before reaching for an electrochemical cell. The next three chapters concern themselves with techniques, starting with hydrodynamic electrodes. Included here we find the rotating disc electrode, of course, but also descriptions of the dropping mercury electrode, as well as wall-jet and channel electrode geometries. Then
ELECTROCHEMICAL AND ELECTROCATALYTIC REACTIONS OF CARBON DIOXIDE Edited by B. P.
SULLIVAN,
K. KRIST
and H. E. GUARD
Elsevier Publishers, Amsterdam, 1993; ISBN O-444-88316-9,ca. E130.
This is, in many ways, a timely book. The electro-reduction of CO,, which is an all but inexhaustible source of carbon, to useful chemical feedstocks has considerable long-term attractions, but the exploratory work that has been carried out over the last 20 years has revealed the immense difli-
cult& that beset the control of multi-step electrochemical processes. It is also important to emphasise that such difficulties are not simply scientific; there are alternatives to the electro-reduction of CO,, the most significant being the direct reduction of CO, by H,. At high temperatures, the
853
854
Book Reviews
equilibrium CO + H,O = CO, + H, lies strongly to the left, and if excess hydrogen is used, chemical reduction to methanol or, with Fischer-Tropsch catalysts, to higher hydrocarbons is possible. Direct electro-reduction of CO, must, then, be competitive with the chemical reduction of CO, by electrolvticallv generated hydrogen, and this book fies&ts a progre& report by a number of North American chemists who have been involved in various aspects of CO, reduction and complexation. The book is, in fact, in two parts, the first of which is primarily concerned with the coordination chemistry of CO, and its reactions with low-valent transitionmetal complexes, and the second is an account of some aspects of the direct electrochemical reduction of CO, at metal and semiconducting electrodes, The coordination chemistry of CO, is well covered, and the two possible routes for CO, uptake, by either direct coordination through mono- or di-hapto ligation or by insertion reactions to yield carboxylato, carbamato or carbonato products, are clearly described and related to the many pathways for transition-metal catalysed CO, reduction that are now known to exist. In this regard, the central chapter in the first section of the book is undoubtedly the fifth, by Keene and Sullivan, which, although covering some of the ground also found in earlier chapters, effectively summa&es the electrocatalytic cycles that have been developed by Ishida, Lehn, Eisenberg and others. For those new to the field, or seeking a good brief introduction, this chapter is ideal. The second half of the book is devoted to three accounts of attempts that have been made to reduce CO, directly at electrode surfaces. The first account, by Frese, is in reality a lengthy report on work carried out in his own group. The report is helpful in that it summa&s a very large amount of data, but the overriding impression left is of how much more will need to be done before the surface chemistry of CO, reduction can be said to be fully understood. Nevertheless, there is much here to stimulate further work and ideas; most valuable without any doubt would be the stimulation of techniques for improved surface characterisation under the highly dynamic conditions operating in the working cells.
Complementary to this chapter is an account by Sammells and Cook of their own recent work on high surfacearea electrodes for CO, reduction. The primary interest of this group has been the reduction of CO, to methane and ethene, particularly on copper electrodes, and this chapter was the only one in the book to address the fundamental problems of engineering the high current density devices that will be needed if the technology is ever to become competitive. Two examples of such technology are given: the use of Na8on electrolytes to fabricate “zero-gap” cells for CO, reduction to CO, CH, and C, hydrocarbons, and the use of perovskite-based catalysts of the form La,_,Sr,CuOs~ to reduce CO, to methanol and higher alcohols. The mechanistic discussion Drovidcd at the end of this chapter is again highly thought-provoking, and an open invitation to devise techniques capable of detecting the many intermediates postulated. Finally, there is an excellent review by Lewis and Shrcve of the photoreduction of CO, both by homogeneous photocatalysis and by illuminated semiconductors. This chapter summarises well the state of knowledge of photocatalysed CO, reduction, and the authors have done a good job in making sense of a literature that is extraordinarily full of contradiction. Any electrochemist hoping to make headway in this area will find this very penetrating account of real value. Taken as a whole, the book is not a comprehensive account; indeed, in so rapidly moving a field it would be impossible to provide such an account, though a more thorough discussion of the immense Japanese effort in the arca could have been provided. The book has clearly been overly long in gestation; a number of articles have 1988 or 1989 as the latest date for references, and this undoubtedly detracts from their timeliness. There is also a considerable amount of repetition in the chapters; editorship has apparently been with a very light hand, as shown by the fact that different chapters have different typefaces. In a book this expensive it is hard to see the justi8cation for not resetting the typescript. The cost of the book certainly places it out of the realms of the private buyer, but it is an indispensable t&e mecum for those interested in CO, chemistry, and is unlikely to be superseded for some time in its specialist niche. A. HAMNETT