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Electrochemical hydrogen technologies. Electrochemical production and combustion of hydrogen
303
J. Electroanal. Chem., 317 (1991) 303-306
Elsevier Sequoia S.A., Lausanne
JEC 01848 Book reviews Electrochemical Hydrogen Technologies. Electrochemical Production and Combustion of Hydrogen. H. Wendt (Editor). Elsevier, Amsterdam, 1990, xx + 512 pp., Dfl.350.00, US$170.00. This book deals with a topic which is generating increased interest all over the world because of the potential impact of hydrogen economy to a cleaner environment. Unlike conference proceedings, this book is very well structured since it covers the fundamentals as well as the technology in a comprehensive manner. The authors of each chapter are mainly from West European academic institutions and industries. In areas where there is less European expertise, leading American academics and industrial scientists have also contributed as joint authors. The book is divided into seven chapters: Chapter 1 deals with the electrode kinetics and electrocatalysis of hydrogen and oxygen electrode reactions. After an excellent introduction on thermodynamic and kinetic considerations, Professor Trasatti of Milan University highlights the important role played by solid state chemistry and materials science in the development of electrocatalysis. This is followed by a comprehensive review of electrocatalysis for cathodic evolution and anodic oxidation of hydrogen by Professor Wendt and Dr. Plzak of Darmstadt Technical University. Apart from a thorough discussion and review of electrode reaction mechanisms, they deal with the preparation, characterisation, microstructure and performance as well as the poisoning of electrode reactions. Therefore, the reader is not merely presented with a collection of factual data but a critical, up-to-date account of the developments in this field. Professor Weisener and Dr. D. Ohms of the Technical University of Dresden follow with a section on oxygen reduction reactions in alkaline and acid media. Apart from discussing the fundamentals of oxygen reduction reactions and the usual catalysts based on precious metal, silver and semiconducting oxides, there is a significant amount of data on macrocylics and heat-treatment of macrocyclics, no doubt due to the fact that the original work on macrocycles started in Eastern Europe. The oxygen evolution reaction in acid and alkaline media is discussed by Professor Trasatti. In recent years, significant progress has been made in elucidation of the mechanism of oxygen evolution and Professor Trasatti has written a very lucid account of the pioneering work done by his group and work done by Professor Tseung’s group at City University, London. The lower oxide/ higher oxide hypothesis on the selection of oxygen evolution electrocatalysis has enabled us to select oxygen evolution electrocatalysts with a far greater degree of confidence then before.
304
Chapter 2 deals with water electrolysis in low and medium temperature regimes. Dr. Divisek of the Physical Chemistry Institute, Julich gives a comprehensive review of commercial electrolysers as well as advanced electrolysis units under development. He also gives a clear account of the principles of electrolyser design. Professor Wendt of Darmstad contributes a section on the economics of hydrogen production, comparing the efficiency and cost of the different electrolysers in use or under development. In addition, the cost of producing hydrogen via reforming of hydrocarbon feedstock is also presented for comparison. The results showed that under normal circumstances, the reforming route is cheaper than the water electrolysis route. However, no consideration of the cost of purifying the hydrogen produced via reforming is taken into account. This could be considerable if the hydrogen has to be purified to a standard acceptable for use in a hydrogen fuel cell. Chapter 3 deals with the status of high temperature water electrolysers and fuel cells. This chapter is written by Drs. Donitz and Erdle of Dornier Ltd and Dr. Streicher of Lurgi Ltd. The use of doped zirconia ceramic tubes as the electrolyte and operating the electrolysers at - lOOo”C, the overvoltage for hydrogen and oxygen evolution is significantly reduced and their results show that the cells can give stable performances over a test period of 3000 h. Since most of the development work on high temperature water electrolysers was done at Dornier and Lurgi, the reader will find much firsthand information on this topic which is not readily available elsewhere. The latter part of this chapter deals with the principles and problems of the high temperature fuel cells based on doped zirconia electrolytes. The pioneering work of Westinghouse Corp. is fully covered as well as recent German studies. The advantages of the solid oxide electrolyte fuel cell is fully described. However, the possible disadvantages, e.g. cost of producing the tubes and poisoning of the electrodes by trace metal impurities in reformed hydrocarbon fuels are not considered. Chapter 4 deals with the production of hydrogen in chlor-alkali cells. Dr. Schmittinger of Huls-Troisdorf AG, wrote this chapter, using the material published in an earlier paper in Ullmann’s Encyclopedia of Industrial Chemistry. Since hydrogen is produced as a by-product in the production of chlorine and sodium hydroxide, I do not see the point in including this chapter in the book; especially since the authors describe the chlor-alkali process in some detail, ranging from diaphragm, mercury and membrane cells. All the modern chlor-alkali plants are based on solid polymer membrane cells and as such the technology is already covered in the earlier chapter. Chapter 5 deals with the thermochemical production of hydrogen. The authors of this chapter, Drs. Struck, Schultz and Van Velzen have been active in the EEC program on hydrogen for many years. The program is based on the scenario in the future where the near-exhaustion of oil and gas force us to rely on nuclear, solar and coal energy sources. The electrolysis of water by conventional electrochemical processes is inherently inefficient since electricity must be produced first. However, if high temperature nuclear reactors or high intensity solar collectors are
305
developed in the future, then it is worth considering hybrid thermochemical cycles, whereby hydrogen halides, e.g. HI, HCl or HBr are first electrolysed to form hydrogen and halides, followed by the high temperature reaction of halides with steam to reform the hydrogen halides. The main advantage of the hybrid cycle is the very much lower voltage required for the electrochemical decomposition of the hydrogen halides ( * 0.7 V) compared to the 1.23 V required for water electrolysis. The work on this subject is still in the earlier stages and no firm conclusion can be drawn on its economic viability; nevertheless, the information in this chapter is of definite interest to those who are involved in hydrogen production research and development. Chapter 6 deals with the novel idea of producing hydrogen by anodic combustion reactions involving the use of powdered coal slurries. Drs. Clark and Foller of Ebonex Technologies Inc. wrote this chapter, based mainly on their own work in this area. The rationale behind their work was to develop a corrosion cell in which the coal is consumed and the counter electrode reaction is hydrogen evolution. In practice, the Fe2+/Fe3+ redox couple is used to assist the anodic oxidation of coal. In practice, though it has been shown that coal can be oxidised under mild conditions, it is doubtful whether such a scheme is practical for the following reasons: (a) poisoning of the electrodes (b) the need to use Nafion@ membranes; (c) purity of the hydrogen produced; (d) lifetime of the systems. Normally, when a process has been developed to a commercial product, it can be called a technology. However, for speculative work or work which is still in its infancy, it is best not to call it a technology and as such should not form a part of a book which has the title “Electrochemical Hydrogen Technologies”. Chapter 7 deals with the conversion of hydrogen in fuel cells. This is a strange title because this chapter deals with hydrocarbon fuels which are reformed to an impure stream of hydrogen and used in phosphoric acid, molten carbonate, and solid oxide electrolyte cells. Dr. Appleby of Texas A&M University and Dr. Selman of the Institute of Gas Technology give a very succinct and well-argued account of hydrogen economy. This is followed by a very detailed description of various alkaline fuel cells by Drs. Winsel of Varta Ltd and Ritcher of Siemens Ltd. Since both authors have extensive experience in development work on alkaline fuel cells by their respective German companies, the chosen material is heavily biased towards German work. However, this may be a useful feature since the English speaking reader is normally not fully aware of the details of German developments during the past twenty years. Drs. Appleby and Selman give a very up-to-date account on the current status of phosphoric acid, molten carbonate and solid oxide electrolyte cells in the United States. In conclusion, despite some minor reservations on the choice of the subject matter, this book should be used by workers in this exciting field since it gives a very comprehensive account of the latest developments as well as sufficient theoretical background to enable those entering this field to understand the subject matter in a short time. A.C.C. TSEUNG Colchester
J. Electroanal. Chem., 317 (1991) 303-306
Elsevier Sequoia S.A., Lausanne
JEC 01848 Book reviews Electrochemical Hydrogen Technologies. Electrochemical Production and Combustion of Hydrogen. H. Wendt (Editor). Elsevier, Amsterdam, 1990, xx + 512 pp., Dfl.350.00, US$170.00. This book deals with a topic which is generating increased interest all over the world because of the potential impact of hydrogen economy to a cleaner environment. Unlike conference proceedings, this book is very well structured since it covers the fundamentals as well as the technology in a comprehensive manner. The authors of each chapter are mainly from West European academic institutions and industries. In areas where there is less European expertise, leading American academics and industrial scientists have also contributed as joint authors. The book is divided into seven chapters: Chapter 1 deals with the electrode kinetics and electrocatalysis of hydrogen and oxygen electrode reactions. After an excellent introduction on thermodynamic and kinetic considerations, Professor Trasatti of Milan University highlights the important role played by solid state chemistry and materials science in the development of electrocatalysis. This is followed by a comprehensive review of electrocatalysis for cathodic evolution and anodic oxidation of hydrogen by Professor Wendt and Dr. Plzak of Darmstadt Technical University. Apart from a thorough discussion and review of electrode reaction mechanisms, they deal with the preparation, characterisation, microstructure and performance as well as the poisoning of electrode reactions. Therefore, the reader is not merely presented with a collection of factual data but a critical, up-to-date account of the developments in this field. Professor Weisener and Dr. D. Ohms of the Technical University of Dresden follow with a section on oxygen reduction reactions in alkaline and acid media. Apart from discussing the fundamentals of oxygen reduction reactions and the usual catalysts based on precious metal, silver and semiconducting oxides, there is a significant amount of data on macrocylics and heat-treatment of macrocyclics, no doubt due to the fact that the original work on macrocycles started in Eastern Europe. The oxygen evolution reaction in acid and alkaline media is discussed by Professor Trasatti. In recent years, significant progress has been made in elucidation of the mechanism of oxygen evolution and Professor Trasatti has written a very lucid account of the pioneering work done by his group and work done by Professor Tseung’s group at City University, London. The lower oxide/ higher oxide hypothesis on the selection of oxygen evolution electrocatalysis has enabled us to select oxygen evolution electrocatalysts with a far greater degree of confidence then before.
304
Chapter 2 deals with water electrolysis in low and medium temperature regimes. Dr. Divisek of the Physical Chemistry Institute, Julich gives a comprehensive review of commercial electrolysers as well as advanced electrolysis units under development. He also gives a clear account of the principles of electrolyser design. Professor Wendt of Darmstad contributes a section on the economics of hydrogen production, comparing the efficiency and cost of the different electrolysers in use or under development. In addition, the cost of producing hydrogen via reforming of hydrocarbon feedstock is also presented for comparison. The results showed that under normal circumstances, the reforming route is cheaper than the water electrolysis route. However, no consideration of the cost of purifying the hydrogen produced via reforming is taken into account. This could be considerable if the hydrogen has to be purified to a standard acceptable for use in a hydrogen fuel cell. Chapter 3 deals with the status of high temperature water electrolysers and fuel cells. This chapter is written by Drs. Donitz and Erdle of Dornier Ltd and Dr. Streicher of Lurgi Ltd. The use of doped zirconia ceramic tubes as the electrolyte and operating the electrolysers at - lOOo”C, the overvoltage for hydrogen and oxygen evolution is significantly reduced and their results show that the cells can give stable performances over a test period of 3000 h. Since most of the development work on high temperature water electrolysers was done at Dornier and Lurgi, the reader will find much firsthand information on this topic which is not readily available elsewhere. The latter part of this chapter deals with the principles and problems of the high temperature fuel cells based on doped zirconia electrolytes. The pioneering work of Westinghouse Corp. is fully covered as well as recent German studies. The advantages of the solid oxide electrolyte fuel cell is fully described. However, the possible disadvantages, e.g. cost of producing the tubes and poisoning of the electrodes by trace metal impurities in reformed hydrocarbon fuels are not considered. Chapter 4 deals with the production of hydrogen in chlor-alkali cells. Dr. Schmittinger of Huls-Troisdorf AG, wrote this chapter, using the material published in an earlier paper in Ullmann’s Encyclopedia of Industrial Chemistry. Since hydrogen is produced as a by-product in the production of chlorine and sodium hydroxide, I do not see the point in including this chapter in the book; especially since the authors describe the chlor-alkali process in some detail, ranging from diaphragm, mercury and membrane cells. All the modern chlor-alkali plants are based on solid polymer membrane cells and as such the technology is already covered in the earlier chapter. Chapter 5 deals with the thermochemical production of hydrogen. The authors of this chapter, Drs. Struck, Schultz and Van Velzen have been active in the EEC program on hydrogen for many years. The program is based on the scenario in the future where the near-exhaustion of oil and gas force us to rely on nuclear, solar and coal energy sources. The electrolysis of water by conventional electrochemical processes is inherently inefficient since electricity must be produced first. However, if high temperature nuclear reactors or high intensity solar collectors are
305
developed in the future, then it is worth considering hybrid thermochemical cycles, whereby hydrogen halides, e.g. HI, HCl or HBr are first electrolysed to form hydrogen and halides, followed by the high temperature reaction of halides with steam to reform the hydrogen halides. The main advantage of the hybrid cycle is the very much lower voltage required for the electrochemical decomposition of the hydrogen halides ( * 0.7 V) compared to the 1.23 V required for water electrolysis. The work on this subject is still in the earlier stages and no firm conclusion can be drawn on its economic viability; nevertheless, the information in this chapter is of definite interest to those who are involved in hydrogen production research and development. Chapter 6 deals with the novel idea of producing hydrogen by anodic combustion reactions involving the use of powdered coal slurries. Drs. Clark and Foller of Ebonex Technologies Inc. wrote this chapter, based mainly on their own work in this area. The rationale behind their work was to develop a corrosion cell in which the coal is consumed and the counter electrode reaction is hydrogen evolution. In practice, the Fe2+/Fe3+ redox couple is used to assist the anodic oxidation of coal. In practice, though it has been shown that coal can be oxidised under mild conditions, it is doubtful whether such a scheme is practical for the following reasons: (a) poisoning of the electrodes (b) the need to use Nafion@ membranes; (c) purity of the hydrogen produced; (d) lifetime of the systems. Normally, when a process has been developed to a commercial product, it can be called a technology. However, for speculative work or work which is still in its infancy, it is best not to call it a technology and as such should not form a part of a book which has the title “Electrochemical Hydrogen Technologies”. Chapter 7 deals with the conversion of hydrogen in fuel cells. This is a strange title because this chapter deals with hydrocarbon fuels which are reformed to an impure stream of hydrogen and used in phosphoric acid, molten carbonate, and solid oxide electrolyte cells. Dr. Appleby of Texas A&M University and Dr. Selman of the Institute of Gas Technology give a very succinct and well-argued account of hydrogen economy. This is followed by a very detailed description of various alkaline fuel cells by Drs. Winsel of Varta Ltd and Ritcher of Siemens Ltd. Since both authors have extensive experience in development work on alkaline fuel cells by their respective German companies, the chosen material is heavily biased towards German work. However, this may be a useful feature since the English speaking reader is normally not fully aware of the details of German developments during the past twenty years. Drs. Appleby and Selman give a very up-to-date account on the current status of phosphoric acid, molten carbonate and solid oxide electrolyte cells in the United States. In conclusion, despite some minor reservations on the choice of the subject matter, this book should be used by workers in this exciting field since it gives a very comprehensive account of the latest developments as well as sufficient theoretical background to enable those entering this field to understand the subject matter in a short time. A.C.C. TSEUNG Colchester