Role of a Hydroxide Layer on Cu Electrodes in ElectrochemicalCO 2 Reduction

Cu is known as one of the most promising metallic catalysts for conversion of CO2 to hydrocarbons such as methane, ethylene, and ethanol by electrochemical reduction. The oxide-derived Cu (OD-Cu) moiety has been investigated as a candidate for enhancing the activity for CO2 electrochemical reduction to C2+ products. The reduction process is affected by catalytic grain boundary, local pH, residual oxygen atoms, and other features of the catalysts. In order to understand the detailed mechanism, we performed in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (in situ ATR-SEIRAS) measurements for CO2 reduction using several different Cu electrodes whose oxidation states are controlled. The spectroscopic investigations demonstrate that a copper oxide electrode (Cu2O) has low activity against CO2 reduction on the basis of low-level detection of CO as an intermediate of CO2 reduction. On the other hand, other Cu electrodes possessing an OH layer on the Cu surface (Cu(OH)2/Cu) a...