Kinetics and mechanism of photo-induced methyl viologen reduction with an organic dye and hydrogen evolution from water by hydrogenase

The formation of the cation radical of methyl viologen was established when an aqueous solution containing an organic dye, methyl viologen, and mercaptoethanol was irradiated by visible light. The reduction of methyl viologen has been studied kinetically and the reduction rate was expressed as follows. where [S], [MV2+], [MV+], and [RSH] are the respective concentrations of the dye photosensitizer, oxidized and reduced forms of methyl viologen, and mercaptoethanol. On the basis of the rate expression, the reaction mechanism is discussed.