Synergistic dual-atom catalysts and water-assisted efficient electrochemical CO₂ reduction to formate

Dual-atom catalysts, which combine the strengths of single-atom catalysts and metal alloys, are considered optimal for facilitating electrocatalytic CO₂ reduction processes. However, developing the means of enhancing the utilization efficiency of bimetallic atoms at catalytic sites and controlling the complex atomic coordination environment to achieve high selectivity and Faradaic efficiency remain a challenge. The present work addresses this issue by synthesizing a bimetallic SnCu-WC_x catalyst via the introduction of individual Sn and Cu atoms supported on a tungsten carbide substrate. High Faradaic efficiencies of 98.62 % and 90.19 % at current densities of 100 and 500 mA cm⁻² for the reduction of CO₂ to formate are respectively achieved through modulation of the coordination environment and electron/proton transfer during catalysis, the creation of shared adsorption sites, and the promotion of synergistic electrocatalysis. The results of operando nuclear magnetic resonance spectroscopy indicate that activated *OH groups are involved in the formation of formate due to the affinity of individual Sn atoms in the SnCu-WC_x catalyst toward *OH. Density functional theory calculations confirm that the presence of individual Sn atoms in SnCu-WC_x promotes the dissociation of H₂O, and thereby modulates the catalytic microenvironment to accelerate the kinetics for the conversion of activated *CO to *COOH groups. Accordingly, the proposed strategy offers new insights into the design of bimetallic catalysts.