A COMPARATIVE-STUDY OF SEMICONDUCTOR PHOTOCATALYSTS FOR HYDROGEN-PRODUCTION BY VISIBLE-LIGHT USING DIFFERENT SACRIFICIAL SUBSTRATES IN AQUEOUS-MEDIA

Different semiconductor photocatalytic systems to produce H2 by visible light have been tested: (1) Pt/TiO2 plus sensitizers like Ru(bipy)32+ and RuL32+ (L = 2,2′-bipyridine-4,4′-dicarboxylate), (2) naked CdS, Pt/CdS and RuO2/CdS, and (3) mixtures of CdS + Pt/TiO2, and CdS and ZnS coprecipitated on γ-Al2O3. EDTA, isopropanol, sulfide and sulfide/sulfite mixtures were used as sacrificial agents. The photocatalytic systems which used sensitizers showed a poor stability and they only produced H2 when EDTA was used as sacrificial agent. The mixture CdS + Pt/TiO2 gave the highest reaction rates for H2 production in isopropanol medium, and CdS, naked or with Pt deposits, produced the best results when sulfide or sulfide/sulfite as sacrificial agents were used. The addition of sulfite to a sulfide aqueous solution increased the H2 production rate about four times with respect to the case when only sulfide was employed. The maximum photochemical and energy efficiencies obtained were 13.2 and 5.0%, respectively, with reference to the wavelength range 300-520 nm. © 1990.