Photocatalysis-The Heterogeneous Catalysis Perspective

Apart from light absorption and charge carrier properties, complete understanding of an active photocatalyst requires consideration of its (surface) structural and catalytic properties. This chapter introduces basic concepts of heterogeneous catalysis and extends them to photocatalysis, highlighting similarities, but also fundamental differences. Two cases of the relevance of catalytic properties for photocatalysis are considered. Focus is put on selective oxidation reactions of alcohols. The case of Au/TiO₂ represents a classical system of a noble metal supported on a semiconductor. Depending on the reaction conditions, gold can function as a true cocatalyst and mainly accelerate the involved surface reactions, or it may also aid in improving light absorption or increasing the amount of charge carriers. As a second example, supported vanadium oxide species on photocatalytically inactive supports are considered. Here, the light absorbing species is at the same time the catalytic active species. It is shown how structural properties affect photocatalytic performance.