Hydrogen production from aqueous mixture of I- and acetonitrile using dye-sensitized Pt/TiO2 photocatalyst was investigated under visible light irradiation. It was found that energetically uphill H-2 formation with a high quantum efficiency (similar to2%) took place using a merocyanine dye-sensitized Pt/TiO2 photocatalyst and an I- electron donor in an acetonitrile-water mixture (AN: H2O = 95:5 by volume) under visible light irradiation (lambda > 440 nm). Addition of acetonitrile, which is a good solvent for I- and merocyanine dye, significantly improved H-2 evolution. (C) 2002 Elsevier Science B.V. All rights reserved.