PHOTOCATALYTIC HYDROGEN-PRODUCTION WITH SEMICONDUCTOR PARTICULATE SYSTEMS - AN EFFORT TO ENHANCE THE EFFICIENCY

Hydrogen production in visible light (lambda = 437 nm) with the following semiconductor particulate systems, Ag(I)/WO3, Fe(III)/WO3 and Cr(III)/WO3 and mixed semiconductors. WO3-CdS and WO3-Pt/CdS, has been investigated in the presence of an electron relay, methylviologen, MV2+. The efficiency of WO3-CdS mixed photocatalyst is found to be less than that of CdS alone. However, Pt loaded CdS powders mixed with WO3 powders (WO3-Pt/CdS) exhibited a notable enhancement in the photocatalytic activity. The effect of sintering temperature on the efficiency of WO3 showed that the sample sintered at 800-degrees-C was with higher efficiency than that sintered at 300-degrees-C. Similarly, loading of WO3 with Ag(I), Fe(III) and Cr(III) by high temperature (800-degrees-C) sintering enhanced the quantum yields when compared to those sintered at 300-degrees-C. Simultaneous use of the electron relay (MV2+) and a hole scavenger (oxalic acid) for water splitting reaction in the presence of Ag(II)/WO3 is found to be less efficient compared to that observed in the presence of MV2+ or oxalic acid alone, which might be due to the interaction of CO2 molecules formed, with methylviologen radical cations.