Sensitization of TiO2 particles by dyes to achieve H2 evolution by visible light

Sensitization of titanium dioxide particles platinized and suspended in water was carried out by Ru(bpy)(3)(2+), tris(bipirimidine)Ru(II) (Ru(bpym)(3)) and porphines to induce dihydrogen evolution by visible light in the presence of sacrificial electron donor, EDTA. It was found that Ru(bpym)(3)(2+) is an efficient sensitizer for H-2 formation. High concentration of the Ru(bpy)(3)(2+) was required to achieve the photosensitization suggesting adsorption of the sensitizer on the TiO2. Photochemical deposition of platinum from K-2[PtCl4] was important to prepare active Pt-loaded TiO2 photocatalyst. Simple mixing of the TiO2 and Pt powders in a mortar as usually done for preparing conventional photocatalyst was not effective for the present system showing that electronic channeling between the TiO2 bulk and the Pt is more important than for usual photocatalysts. The H-2 evolution showed an optimum point at pH 7, which was interpreted by the adsorption of the dye on TiO2. For the tetrakis(4-carboxyphenyl)porphine and tetrakis(4-sulfonicphenyl)porphine sensitizers, only the absorption of light at Q band was effective. (C) 2000 Elsevier Science S.A. All rights reserved.