CHAPTER 9. Interplay Between Physical and Chemical Events in Photoprocesses in Heterogeneous Systems

Abstract

The principal objectives of this chapter are to demonstrate those interplay phenomena that take place between physical and chemical events in heterogeneous photochemistry and photocatalysis through an examination of some relevant processes starting from the initial photoexcitation of solids to subsequent events occurring on absorption of photons by semiconductor/insulator photoactive materials, followed by competition and interconnection between physical and chemical relaxation of heterogeneous systems. Particular examples of such interplay are presented as a competition between physical and chemical decay of the active state of surface-active centers through charge recombination and chemical interaction, as an effect of catalytic and non-catalytic surface photochemical processes on the photostimulated formation of defects, and the interconnection between photocatalyst activity and selectivity. It is deduced that the creation of new generations of photoactive materials will lead to successful applications if and only if such interplay between physical and chemical processes is fully taken into account.