Homogeneous and Heterogeneous Photocatalysis

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.

Photoinduced charge separation: Requirements needed for ideal relays and photosensitizers.- Photoinduced charge separation: Towards the design of supermolecular systems based on transition metal complexes.- Fundamental studies into primary events in photocatalysis employing CdS and TiO semiconductors: Photoluminescence, laser flash photolysis and pulse radiolysis.- Dynamics of interfacial electron transfer reactions in colloidal semiconductor systems and water cleavage by visible light.- Electronic Spectroscopy of semiconductor clusters.- Catalysed decay of oxidising radicals in water.- Photocatalysis and light—induced electron transfer reactions of tertiary amines.- Photocatalytic production of ascorbic acid. A secondary photosynthesis in plants.- Spectroscopic and electrochemical studies of photochemical electron transfer in linked donor—acceptor molecules.- Bifunctional porphyrins: Redox photochemistry of: meso(tritolyl(pyridyl Ru(III) (NH 3) 4 L’)) porphyrin: (L’=NH 3, pyridine, 5-Cl-pyridine).- Linear chain platinum complexes as photocatalysts.- Electron transfer reactions on extremely small semiconductor colloids studied by pulse radiolysis.- Nafion stabilized aqueous solutions of colloidal semiconductors.- In situ generated catalyst-coated colloidal semiconductor CdS particles in surfactant vesicles and polymerized surfactant vesicles.- Development of catalysts for water photoreduction: Improvement, poisoning and catalytic mechanism.- Radiolytic methods of preparation of colloidal and heterogeneous redox catalysts and their application in light-induced H2 generation from water.- The effect of promoters on the photochemical water cleavage in suspensions of Pt-loaded TiO2 with increased light to chemical conversion efficiency.- Metallic catalysts on semiconductors: Transparency and electrical contact properties.- On the nature of the inhibition of electron transfer at illuminated p-type semiconductor electrodes.- The importance of solution kinetics in photoelectrochemical phenomena.- Mechanistic aspects of semiconductor photoelectrochemistry: The behavior of Si and GAAs in nonaqueous solvents.- Charge injection into semiconductor particles — Importance in photocatalysis.- Hydrogen evolution and selective organic photosynthesis catalyzed by zinc sulfide.- Photocatalytic organic synthesis by use of semiconductors or dyes.- A. Hiskia and A. Ioannidis Photocatalytic oxidation of organic compounds with heteropoly electrolytes. Aspects on photochemical utilization of solar energy.- Photoformation of hydrogen in liquid water in the presence of Pt/TiO2 catalyst and organic impurities.- Surface properties of catalysts. Iron and its oxides: Surface chemistry, photochemistry and catalysis.- Photocatalysis over clay supports.- Photoreduction and-oxidation of molecular nitrogen on titanium dioxide and titanium containing minerals.- Photoassisted reduction of carbon and nitrogen compounds: with semiconductors.- Adsorption and desorption processes in photocatalysis.- Photo-induced processes at titanium dioxide surfaces.- Photolysis of adsorbed phases: Ethanoic acid-insulators and semiconductors systems. Influence of acid-base properties.- Cadmium sulfide photocatalyzed hydrogen production from aqueous solutions of sulfite.- Environmental photochemistry of chlorinated aromatics in aqueous media. A review of data.- Photodegradation of wastes and pollutants in aquatic environment.- Heterogeneous photocatalysis for water purification: Prospects and problems.- A Gas Research Institute perspective on inorganic synthesis of gaseous fuels.- Putting photocatalysis to work.- Panel discussion on the Selective activation and conversion of molecules.- Panel discussion on Sensitization and immobilization of catalysts on various supports.- Panel discussion on Electrocatalysis and photocatalysis.- Final Remarks.- Author Index.