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.