Proflavin Catalyzed Photoproduction of Hydrogen From Organic Compounds

Abstract

Methyl viologen was reduced by EDTA and other organic compounds when aqueous solutions of these compounds were irradiated near 440 nm in the presence of catalytic quantities of proflavin. The photoreduced methyl viologen was readily oxidized in the dark by the enzyme hydrogenase or platinum asbestos. When the entire reaction was run in the light with hydrogenase or platinum, continuous production of hydrogen was observed. The yield of hydrogen was approximately stoichiometric to the EDTA present establishing that methyl viologen and proflavin were acting catalytically. To establish the structural requirements of the electron donor, eighty compounds were tested at seven pH values between 4 and 10. Of these, twenty served as electron donors for the photoproduction of hydrogen. The effective donors contained either a secondary or tertiary nitrogen atom with one or more carboxymethyl or b-hydroxyethyl groups, or a sulfhydryl group. The system could also reduce benzyl viologen but not methylene blue. Riboflavin did not replace proflavin for the photoproduction of hydrogen, This system may have potential for producing hydrogen with solar energy.

Ligand Variations in [ReX(diimine)(CO)3] Complexes: Effects on Photocatalytic CO2 Reduction

“…[31] None of these donors caused any quenching of [ReX(diimine)(CO) 3 ] fluorescence in solution, although all meet the requirements of a thermodynamically accessible, irreversible oxidation. [31] Photochemical CO 2 Reductions: Experiments to study the photocatalytic activity of these complexes in the Strasbourg system were carried out under conditions similar to the reported set-up. [10] Only CO with no detectable quantities of H 2 was found in the headspace of the reaction solutions.…”

Photoactive Modified Hydroxyethylcellulose

“…Irradiation of the aqueous solution containing HENC, TEA, and MVCl 2 was carried out in a Rayonet photochemical reactor equipped with RPR-3500 lamps (maximum emission at 350 nm, see Figure 1). The radiation, selectively absorbed by Np, brings about the formation of semi-reduced viologen, MV .þ , which is characterized by the absorption bands at 395 and 600 nm [10] (see Figure 4). Electron transfer from Np to MV 2þ was followed by measuring the changes in the absorbance of MV .þ at 394 nm occurring during irradiation.…”

Photoelectrochemical studies on [MnMoO2(NCS)(Ox)3(H2O)2] (Ox=8-quinolinol): a novel system for solar energy conversion

“…Photogalvanic cells are one such type in which certain species dissolved in a suitable solvent are the light absorbing ones (Wrighton, 1983). Various photogalvanic cells are reported in the literature (Ameta et al, 1985(Ameta et al, , 1991Baumgartner et al, 1981;Dube, 1993;Dube et al, 1993;Eisenberg and Silverman, 1961;Gangotri et al, 1996;Kamat et al, 1978;Kaneko and Yamada, 1977;Krasna, 1979;Khamesra et al, 1989;Moorthy et al, 1980;Oster and Adelman, 1956;Quickenden and Yim, 1977;Rabinowitch, 1940;Rohatgi-Mukherjee et al, 1983;Wildes et al, 1977) and cells using inorganic compounds/complexes are very rare. We have already reported (Suresh et al, 1999) the photovoltage generation of [MnMoO (Et dtc) (H O)] in solution and solid state, with a maximum photovoltage of 1.08 V and 80 A current, when studied in a photoelectrochemical cell.…”