Selective Enhancement of Methane Formation in Electrochemical CO2 Reduction Enabled by a Raman-Inactive Oxygen-Containing Species on Cu

The role of oxygen-containing species on Cu catalysts in the electrochemical CO2 reduction reaction (CO2RR) remains unclear due to the difficulty in its stabilization under reaction conditions. Co-electrolysis of CO2 with an oxidant is an effective strategy to introduce oxygen-containing species on Cu during the CO2RR. In this work, we present concrete evidence demonstrating that an oxygen-containing species is able to not only enhance the rate of the CO2RR but also tune selectivities for certain products. Co-electrolysis of CO2 with H2O2 on Cu selectively accelerates the CH4 production rate by up to a factor of 200, but with only a slight enhancement of C2+ products. Combined investigations using in situ Raman spectroscopy with density functional theory calculations reveal that a Raman-inactive Cu oxide species is responsible for the improved CH4 production. Results reported in this work highlight the possibility of enhancing Cu-based CO2RR catalysts by introducing stable oxygen-containing catalytic structures.