Dye-sensitized photocatalysts for efficient hydrogen production from aqueous I- solution under visible light irradiation

H-2 production from a water-acetonitrile (AN) mixed solution containing iodide electron donor was investigated over dye-sensitized Pt/TiO2 photocatalysts under visible light irradiation. It was found that H-2 production with good quantum efficiency (similar to2.5%) took place using merocyanine and coumarin dye-sensitized Pt/TiO2 photocatalysts, respectively, and an I- electron donor in a water-acetonitrile mixture (water, 5% by volume). The rates of H-2 evolution were decreased with the increase of the water amount in the mixed solution because of the decrease in energy gap between the redox potential of I-3 (-)/I- and the HOMO level of the dye. H-2 evolution was also decreased with the accumulation of produced I-3(-) from I-. However, we have also found that it is possible to prevent the backward reaction, reduction of I-3(-) to I- on Pt metal by using the internally platinized semiconductor K4Nb6O17 instead of Pt/TiO2 in water-AN mixed solution. (C) 2004 Elsevier B.V. All rights reserved.