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

Abstract

Carbon dioxide (CO₂) 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 CO₂ into CO or HCOOH using a copper sulfide-loaded copper foam (Cu₂S/CF) self-supporting electrode. Cu₂S/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 Cu⁰ under the applied potential of −0.4 V vs. RHE forming vacancy S defects (V_S) in Cu₂S. Notably, the Cu₂S/CF achieve a potential regulable electroreduction CO₂ 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 CO₂ adsorption configurations of catalytic centers resulting in the difference on the reduction products. Saturation Cu site on Cu₂S surface favours to adsorb CO₂ with end-on configuration of *COOH for CO production, and unsaturation Cu site on Cu₂S-V_S surface prefers to the bridge configuration of *O*COH for HCOOH synthesis.