Modulating the Coordination Environment of Cu-Embedded Mo ( = S, Se, and Te) Monolayers for Electrocatalytic Reduction of CO to CH: Unveiling the Origin of Catalytic Activity.

The electrochemical CO reduction reaction (CORR) is a promising approach to alleviating global warming and emerging energy crises. Yet, the CORR efficiency is impeded by the need for electrocatalysts with good selectivity and efficiency. Recently, single-atom catalysts (SACs) have attracted much attention in electrocatalysis and are more efficient than traditional metal-based catalysts. In this study, we modeled a Cu single atom embedded on Mo ( = Se and Te) monolayer with a single chalcogen () vacancy as SAC. Employing the dispersion-corrected density functional theory (DFT-D3) method, the electrocatalytic CORR activity of the Cu-Mo SACs is systematically investigated through significant descriptors, such as the Gibbs free energy change, charge density difference, and COHP analysis. The stability of SACs, CO adsorption configurations, and all possible reaction pathways for the formation of C1 products (HCOOH, CO, CHOH, and CH) were examined. All of the Cu-Mo SACs are stable and show high catalytic selectivity for the CORR by significantly suppressing the hydrogen evolution reaction (HER). We found that the catalytic activity is mainly due to the level of antibonding states filling between the Cu atom and *OCHOH intermediate. Among the C1 products, CH is selectively produced in all three SACs. Notably, there is a decrease in the limiting potential () when changes from S to Te in Cu-Mo. Among these three SACs, Cu-MoTe SAC is the most promising catalyst for reducing CO to CH, with as low as of -0.34 V vs RHE. Our results demonstrate that the local coordination environment in SACs has a significant impact on the catalytic activity of CORR.