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Photoinduced reduction of formate to methanol has been achieved using ZnS microcrystalline colloid which contained formate, methanol dehydrogenase (MDH), pyrroloquinoline quinone (PQQ) as an electron mediator for MDH, and 2propanol. This reaction was combined with photoreduction of carbon dioxide to formate on the ZnS microcrystallite which had already been reported to provide a new photosynthetic route for production of methanol from carbon dioxide. The production of methanol showed a saturation tendency when it was accumulated to 0.25 mmol dm -3, probably due to oxidation of the produced methanol at MDH or on the ZnS photocatalyst or both. The concentration of PQQ influenced the amount of formate production but not the methanol production. The quantum efficiency obtained at 280 nm for the reduction of carbon dioxide to methanol was 5.9%, which is the highest value that has ever been reported for the photochemical reduction of carbon dioxide to methanol.

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Electrolysis of carbon dioxide-saturated phosphate buffer solution (pH 7) in the presence of formate dehydrogenase and methanol dehydrogenase as electrocatalysts together with methylviologen as an electron relay yielded formaldehyde and methanol as the reduction products of carbon dioxide under suitable electrolysis conditions, and the use of pyrrolo-quinoline quinone in place of methylviologen as the electron relay afforded selective reduction of carbon dioxide to methanol.

Various platinum (Pt) colloid solutions were prepared and used for the modification of n-type silicon (n-St) electrodes. All the photoelectrochemical (PEC) solar cells, equipped with the Pt-colloid modified n-St electrodes thus prepared, gave the open-circuit photovoltages (Voo) of 0.550 to 0.630 V, much higher than those (0.25 ~ 0.30 V) for n-St electrodes coated with continuous thin Pt layers, clearly showing the beneficial effect of the discontinuous metal coating. The PEC cells, equipped with the textured-surface n-St electrodes modified with the Pt colloid particles prepared by Bredig's method, yielded an energy conversion efficiency of 14.9% in a three-electrode configuration. The relation between the Voc and the size and distribution of the Pt particles is discussed.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.160.4.77 Downloaded on 2015-03-30 to IP