Surface reconstruction of copper(Ⅰ) sulfide electrode regulated electroreduction CO2 selectivity

Carbon dioxide (CO 2 ) electroreduction to valuable chemicals is a promising approach for efficient carbon utilization. Herein, we propose an in situ electrochemical reconstruction method to regulate the selectivity of electroreduction of CO 2 into CO or HCOOH using a copper sulfide-loaded copper foam (Cu 2 S/CF) self-supporting electrode. Cu 2 S/CF under the applied potential of −0.2 V versus reversible hydrogen electrode (vs. RHE) maintain as the intial one, and Cu + are partially reduced to Cu 0 under the applied potential of −0.4 V vs. RHE forming vacancy S defects (V S ) in Cu 2 S. Notably, the Cu 2 S/CF achieve a potential regulable electroreduction CO 2 into CO with faradaic efficiency (FE) of 84.6 % at the applied potential of −0.2 V vs. reversible hydrogen electrode (RHE) and HCOOH with FE of 81.6 % at −0.4 V vs. RHE. Density functional theory (DFT) calculations reveal the different CO 2 adsorption configurations of catalytic centers resulting in the difference on the reduction products. Saturation Cu site on Cu 2 S surface favours to adsorb CO 2 with end-on configuration of *COOH for CO production, and unsaturation Cu site on Cu 2 S-V S surface prefers to the bridge configuration of *O*COH for HCOOH synthesis.