Electrochemical reduction of CO2 on hydrogen-enriched and hydrogen-depleted surfaces

Abstract

A cell using Pd foil is proposed for investigating the mechanism of electrochemical reduction where surface hydrogen activity is controlled separately from the potential. Hydrogen is supplied to the surface from behind by reverse-face electrolysis (hydrogen-enriched surface) but, without this electrolysis, hydrogen is removed from the surface by absorption by Pd (hydrogen-depleted surface). In the electrochemical reduction of CO₂ on a hydrogen-enriched surface at 298 K, the current efficiency of HCO₂H was enhanced more than 2000-fold (less than 0.01% to 21%) while that of CO was suppressed a little, compared with the reduction on a hydrogen-depleted surface. The reaction mechanism is discussed in relation to the role of surface hydrogen, on the basis of current–potential plots and the amount of hydrogen formed during the electrolysis.