Photocatalysis on Solid Catalysts

Irradiation of a semiconductor photocatalyst with light of appropriate wavelength results in the excitation of an electron from the valence band into the conduction band, leaving a positively charged hole in the valence band. This electron then can be transferred to an electron acceptor whereas an electron from a donor recombines with the hole in the valence band. In this manner, redox reaction can be catalyzed on the surfaces of semiconductors, such as for example TiO₂ or ZnO. Combining semiconductor properties with specific steric arrangements within the pores of nanoporous solids appears a promising approach to tune the photocatalytic properties of such solids.