Preparation of egg-shell type Al2O3-supported US photocatalysts for reduction of H2O to H2

Alumina-supported cadmium sulfide photocatalysts were prepared for the photocatalytic reduction of water to hydrogen using visible light. The activity depends on the nature of interaction between alumina and cadmium and also on the distribution of US on the support. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen desorption and temperature-programmed oxidation. The impregnation of alumina hydrogel with an ammoniacal solution results into a chemical interaction between cadmium sulfide and alumina and also yields a preferential distribution of cadmium sulfide on the surface which give a better activity to the photocatalyst. The possible role of ammonia in causing the solute segregation to the surface during the drying stage of the catalyst preparation has been explained. (C) 2001 Elsevier Science BN. All rights reserved.