ELECTROCHEMICAL EVIDENCE OF INTERMEDIATE FORMATION OF ADSORBED CO IN CATHODIC REDUCTION OF CO2 AT A NICKEL ELECTRODE

Electroreduction of CO2 and CO was studied with voltammetric and coulometric measurements in aqueous electrolytes. The reaction products as well as their distribution are similar both for CO2 and CO. CO is strongly adsorbed on Ni from a CO saturated electrolyte; adsorbed CO is not desorbed, even when dissolved CO is purged by sparging Ar in the solution. Adsorbed CO prevents significant hydrogen evolution in the cathodic region. The oxidative dissolution of the Ni electrode is markedly suppressed by adsorbed CO in the anodic region as well. Adsorbed CO is anodically oxidized at +0.12V vs nhe. On the basis of coulometric measurements, it was presumed in our previous reports that the electroreduction of CO2 proceeds with intermediate formation of CO. The chemical species formed during the reduction of CO2 on Ni electrode showed identical behavior with adsorbed CO. © 1990.