A comparative study of semiconductor photocatalysts for hydrogen production by visible light using different sacrificial substrates in aqueous media

Abstract Different semiconductor photocatalytic systems to produce H 2 by visible light have been tested: (1) Pt/TiO 2 plus sensitizers like Ru(bipy) 3 2+ and RuL 3 2+ (L = 2,2′-bipyridine-4,4′-dicarboxylate), (2) naked CdS, Pt/CdS and RuO 2 /CdS, and (3) mixtures of CdS + Pt/TiO 2 , and CdS and ZnS coprecipitated on γ-Al 2 O 3 . 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 H 2 when EDTA was used as sacrificial agent. The mixture CdS + Pt/TiO 2 gave the highest reaction rates for H 2 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 H 2 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.