HOMOGENEOUS CATALYSIS IN THE MEDIATED ELECTROCHEMICAL REDUCTION OF CARBON-DIOXIDE

Electrochemical reduction of CO2 via homogeneous catalysis at a mediated electrode has been studied, and the function of the homogeneous catalyst as well as the electrode mediator revealed. The homogeneous catalyst used was a system consisting of cobalt(II)-2-nitroso-1-naphthol-4-sulfuric acid (L) complex and methanol, and the electrode mediator was Everitt's salt film (ES, K2Fe(II)[Fe(II)(CN)6]). The total electron-transfer reaction was the reduction of CO2 to methanol. The reaction rate was determined by the insertion of CO2 into the Co(I)-oxygen(methanol) bond, and the rate constant was estimated 2 X 10(-5) cm s-1. The cobalt complex carrying CO2 exhibited the catalytic effect by adsorbing onto the ES film and accepting electrons from the cathode. It was suggested that an electron channel was built up at a localized site extending from the mediated cathode to the adsorbed complex where electrons were delivered to CO2.