Highly Selective Electrochemical Reduction of CO(2) into Methane on Nanotwinned Cu

[Image: see text] The electrochemical carbon dioxide reduction reaction (CO(2)RR) is a promising route to close the carbon cycle by reducing CO(2) into valuable fuels and chemicals. Electrocatalysts with high selectivity toward a single product are economically desirable yet challenging to achieve. Herein, we demonstrated a highly (111)-oriented Cu foil electrocatalyst with dense twin boundaries (TB) (tw-Cu) that showed a high Faradaic efficiency of 86.1 ± 5.3% toward CH(4) at −1.2 ± 0.02 V vs the reversible hydrogen electrode. Theoretical studies suggested that tw-Cu can significantly lower the reduction barrier for the rate-determining hydrogenation of CO compared to planar Cu(111) under working conditions, which suppressed the competing C–C coupling, leading to the experimentally observed high CH(4) selectivity.