Hydrogen Evolution from Water by Visible Light,a Homogeneous Three Component Test System for Redox Catalysis

Irradiation by visible light of a neutral aqueous solution containing Ru (bipy) as a sensitizer, methylviologen (MV⁺²) as an electron acceptor and triethanolamine or cysteine as an electron donor leads to the formation of stable methylviologen radical cation (MV⁺). The kinetics and mechanism of the photoinduced reactions occurring in such a system were explored by laser photolysis technique. In the presence of Adams catalyst MV⁺ is reoxidized by water under simultaneous evolution of hydrogen. Optimum conditions for the water reduction under continuous illumination are elaborated and implications for an energy conversion system discussed.