Bi/CeO2–Decorated CuS Electrocatalysts for CO2-to-Formate Conversion

The electrocatalytic carbon dioxide (CO2) reduction reaction (CO2RR) is extensively regarded as a promising strategy to reach carbon neutralization. Copper sulfide (CuS) has been widely studied for its ability to produce C1 products with high selectivity. However, challenges still remain owing to the poor selectivity of formate. Here, a Bi/CeO2/CuS composite was synthesized using a simple solvothermal method. Bi/CeO2–decorated CuS possessed high formate selectivity, with the Faraday efficiency and current density reaching 88% and 17 mA cm−2, respectively, in an H-cell. The Bi/CeO2/CuS structure significantly reduces the energy barrier formed by OCHO*, resulting in the high activity and selectivity of the CO2 conversion to formate. Ce4+ readily undergoes reduction to Ce3+, allowing the formation of a conductive network of Ce4+/Ce3+. This network facilitates electron transfer, stabilizes the Cu+ species, and enhances the adsorption and activation of CO2. Furthermore, sulfur catalyzes the OCHO* transformation to formate. This work describes a highly efficient catalyst for CO2 to formate, which will aid in catalyst design for CO2RR to target products.