Shin Kusunoki

Photoreduction of viologens and hydrogen evolution with hydrogenase

Abstract Ethyl-, propyl-, and n-butyl-viologens are found to be electron carries for photoinduced hydrogen production and also can be cofactors of hydrogenase. As these viologens are photoexcited by visible light irradiation or sunlight, simpler systems without another photosensitizer can be developed for the photochemical utilization of solar energy.

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. On the addition of hydrogenase to the above photoirradiation system, hydrogen evolution was observed by the irradiation of visible light.

Comparison of activities for hydrogen evolution from water of hydrogenase and colloidal platinum

The activities for hydrogen evolution from water were compared for both hydrogenase and colloidal platinum and the turnover number per active site of hydrogenase was 500 times larger than that for colloidal platinum.