Mechanistic Insights for Low-Overpotential Electroreduction of CO2 to CO on Copper Nanowires

Recent developments of copper (Cu)-based nano materials have enabled the electroreduction of CO2 at low overpotentials. The mechanism of low-overpotential CO2 elusive. We report here a systematic investigation of CO2 reduction on highly dense Cu nanowires, with the focus placed on understanding the surface structure effects on the formation of *CO (*denotes an adsorption site on the catalyst surface) and the evolution of gas-phase CO product (CO(g)) at low overpotentials (more positive than -0.5 V). Cu nanowires of distinct nanocrystalline and surface structures are studied comparatively to build up the structure property relationships, which are further interpreted by performing density functional theory (DFT) calculations of the reaction pathway on the various facets of Cu. A kinetic model reveals competition between CO(g) evolution and *CO poisoning depending on the electrode potential and surface structures. Open and metastable facets such as (110) and reconstructed (110) are found to be likely the active sites for the electroreduction of CO2 to CO at the low overpotentials.