A metallic Cu2N monolayer with planar tetracoordinated nitrogen as a promising catalyst for CO2 electroreduction

Abstract

The electrochemical carbon dioxide reduction reaction (CO₂RR) holds great promise for mitigating CO₂ emission and simultaneously generating high energy fuel. However, it remains a great challenge to reduce CO₂ to C₂ products due to the lack of highly efficient catalysts. Herein, by means of a particle swarm optimization search and comprehensive density functional theory (DFT) computations, we predicted a hitherto unknown Cu₂N monolayer with planar hexacoordinate Cu and tetracoordinate N atoms as a CO₂RR catalyst. Our results revealed that the Cu₂N monolayer shows outstanding stability and intrinsic metallicity. Interestingly, the as-designed Cu₂N monolayer exhibits superior CO₂RR catalytic performance with a rather low limiting potential (−0.33 V), resulting in the formation of a C₂H₄ product with a small kinetic barrier (0.55 eV) for the coupling between *CH₂ and a CO molecule. Strikingly, the N atoms within the Cu₂N monolayer were revealed to be the CO₂RR active sites due to their significant binding strength with the CO₂RR species and their significant spin moments. Our findings not only propose a useful roadmap for the discovery of 2D hypercoordinate materials, but also provide cost-effective opportunities for advancing sustainable CO₂ conversion.