Hydrogen production in visible light (λ = 437 nm) with the following semiconductor particulate systems, Ag(I)/WO3, Fe(III)/WO3and Cr(III)/WO3and 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 WO3powders (WO3-Pt/CdS) exhibited a notable enhancement in the photocatalytic activity. The effect of sintering temperature on the efficiency of WO3showed that the sample sintered at 800°C was with higher efficiency than that sintered at 300°C. Similarly, loading of WO3with Ag(I), Fe(III) and Cr(III) by high temperature (800°C) sintering enhanced the quantum yields when compared to those sintered at 300°C. Simultaneous use of the electron relay (MV2+) and a hole scavenger (oxalic acid) for water splitting reaction in the presence of Ag(I)/WO3is 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 CO2molecules formed, with methylviologen radical cations. © 1991.
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