Energy Resources through Photochemistry and Catalysis reviews the state of the art in the development of energy conversion devices based on catalytic and photochemical reactions. The focus is on catalysis of redox reactions and their application to the photocleavage of water, reduction of carbon dioxide, and fixation of nitrogen. Some fundamental aspects of catalysis as it relates to processes of light energy harvesting and charge separation in photochemical or photoelectrochemical conversion systems are also discussed. This monograph is comprised of 16 chapters covering light-induced redox reactions and reaction dynamics in organized assemblies such as micelles, colloidal metals, or semiconductors, together with strategies for molecular engineering of artificial photosynthetic devices. The principles of electrochemical conversion of light energy via semiconductor electrodes or semiconducting particles are also considered. Furthermore, thermodynamic characteristics for some reactions that can be utilized for storage of solar energy in the form of chemical energy are examined. The remaining chapters look at the role of porphyrins in natural and artificial photosynthesis; the use of semiconductor powders and particulate systems for photocatalysis and photosynthesis; and hydrogen-generating solar cells based on platinum-group metal activated photocathodes. This text will be a useful resource for scientists and policymakers concerned with finding alternative sources of energy.

Ever since the oil crisis of 1973, researchers in various fields of chemistry have proposed various schemes to conserve energy, as well to convert the sun's abundant and limitless supply of energy to produce chemical fuels (e. g. , hydrogen from water, . •. ). The enthusiasm had no previous parallel in the mid-1970's. Unfortunately, despite the several good proposals, the results have proven - in retrospect - somewhat disappointing from an economic viable point of view. The reasons for the meagre results are manyfold not the least of which are the experimental difficulties encountered in storage systems. Moreover, the lack of a concerted, well orchestrated interdisciplinary approach has been significant. By contrast, the chemical advances made in the understanding of the processes involved in such schemes have been phenomenal. A recent book on this issue ( M. Gratzel, Energy Resources through Photochemistry and Catalysis, 1983) is witness to the various efforts and approaches taken by researchers. In the recent years, many more groups have joined in these efforts, and the number of papers in the lit~rature is staggering ! One of the motives for organizing this NATO Advanced Research Workshop stemmed from our view that it was time to take stock of the accomplishments and rather than propose new schemes, it was time to consider seriously avenues that are most promising.

This book collects the lectures delivered by the Authors during the NATO ASI "Fundamentals and Developments of Photocatalytic and Photoelectrochemical Processes", held in Erice (Trapani, Italy) from May 20th to June 2nd 1984. The ASI was devoted to the general field of photochemical conversion and storage of solar energy. It had the aim of defining the "state of art" and of outlining perspectives, lines of development and practic al utilization of this form of energy. The world energy crisis has stimulated scientists to investigate new routes for finding and testing methods and processes for obtaining renewable and cheap sources of energy. Within this framework, the possibility of solar energy utilization on a large scale must overcome the stage of discovering efficient processes for the photochemical conversion and for the storage. The most promising way for achieving this goal seems the photosplitting of water and related reactions. The methods for obtaining the water photosplitting are essentially based on photoelectrochemical cells and on photocatalytic systems (gas-solid and gas-liquid-solid). Extensive research work is currently done all over the world both in universities and in industrial laboratories in these areas. The ASI has given to the audience a general view of the fundamental aspects and as much as possible a detailed insight of the various methods and processes. A section has been also devoted to the photoreactors, a field in which the interest is ix x FOREWORD steadily increasing and whose development is essential for the practical exploitation of the various methods.

This workshop comprises part of the four-year (1985-1988) non-nuclear energy R & D programme for the development of renewable energy sources which is being implemented by the Commission of the European Communities. The aim of the workshop was to present work by the contracting laboratories in addition to work by numerous other research laboratories in 11 European countries. Extensive discussions were also held on the present state of this basic, directed research in photochemistry, photoelectrochemistry and photobiology, and where the future emphasis may usefully lie. Thus the book presents the proceedings of all the papers presented and summarizes the recommendations made by the participants as to where future research support may be most effectively placed. It was emphasized in these recommendations that the interdisciplinary collaboration between photochemistry and photobiology had been quite successfully achieved in this European programme. There were both high quality basic research and practical benefits accruing from the work, and these are described in the report on proposed areas for future research. This book contains work reported by 30 leading researchers and laboratories in Europe. The contents parallels and overlaps research in photovoltaics and semiconductors and therefore provides a unique link and basis of information across the field of photovoltaics, semiconductors and photosynthesis.

This workshop comprises part of the four-year (1985-1988) non-nuclear energy R & D programme for the development of renewable energy sources which is being implemented by the Commission of the European Communities. The aim of the workshop was to present work by the contracting laboratories in addition to work by numerous other research laboratories in 11 European countries. Extensive discussions were also held on the present state of this basic, directed research in photochemistry, photoelectrochemistry and photobiology, and where the future emphasis may usefully lie. Thus the book presents the proceedings of all the papers presented and summarizes the recommendations made by the participants as to where future research support may be most effectively placed. It was emphasized in these recommendations that the interdisciplinary collaboration between photochemistry and photobiology had been quite successfully achieved in this European programme. There were both high quality basic research and practical benefits accruing from the work, and these are described in the report on proposed areas for future research. This book contains work reported by 30 leading researchers and laboratories in Europe. The contents parallels and overlaps research in photovoltaics and semiconductors and therefore provides a unique link and basis of information across the field of photovoltaics, semiconductors and photosynthesis.