Structure–activity relationship of Cu-based catalysts for the highly efficient CO2 electrochemical reduction reaction

Electrocatalytic carbon dioxide reduction (CO 2 RR) is a relatively feasible method to reduce the atmospheric concentration of CO 2 . Although a series of metal-based catalysts have gained interest for CO 2 RR, understanding the structure–activity relationship for Cu-based catalysts remains a great challenge. Herein, three Cu-based catalysts with different sizes and compositions (Cu@CNTs, Cu 4 @CNTs, and CuNi 3 @CNTs) were designed to explore this relationship by density functional theory (DFT). The calculation results show a higher degree of CO 2 molecule activation on CuNi 3 @CNTs compared to that on Cu@CNTs and Cu 4 @CNTs. The methane (CH 4 ) molecule is produced on both Cu@CNTs and CuNi 3 @CNTs, while carbon monoxide (CO) is synthesized on Cu 4 @CNTs. The Cu@CNTs showed higher activity for CH 4 production with a low overpotential value of 0.36 V compared to CuNi 3 @CNTs (0.60 V), with *CHO formation considered the potential-determining step (PDS). The overpotential value was only 0.02 V for *CO formation on the Cu 4 @CNTs, and *COOH formation was the PDS. The limiting potential difference analysis with the hydrogen evolution reaction (HER) indicated that the Cu@CNTs exhibited the highest selectivity of CH 4 among the three catalysts. Therefore, the sizes and compositions of Cu-based catalysts greatly influence CO 2 RR activity and selectivity. This study provides an innovative insight into the theoretical explanation of the origin of the size and composition effects to inform the design of highly efficient electrocatalysts.