Electrochemical reduction of carbon dioxide at a platinum electrode in acetonitrile-water mixtures

Electrochemical reduction of CO2 was studied in 0.1 M TEAP acetonitrile-water mixtures. Pt, inert in the electrochemical reduction of CO2 in aqueous media, can reduce CO2 to oxalic acid in water free acetonitrile. With the increase of water concentration, oxalic acid formation dropped and the yield of formic acid increased. CO2 reduction was suppressed with further increase of water concentration. The presence of adsorbed CO was confirmed on the Pt electrode surface by in-situ FT-IR spectroscopy. The Pt electrode covered with adsorbed CO reduce CO2 apparently in a similar way with sp-metal electrodes. The reaction intermediate CO2 .(-) is not adsorbed on the electrode surface, and the major products are oxalic acid and formic acid in accordance with the reaction mechanism previously proposed by the present authors.