The role of copper in enhancing the performance of heteronuclear diatomic catalysts for the electrochemical CO2 conversion to C1 chemicals

Diatomic catalysts (DACs) with two adjacent metal atoms supported on graphene can offer diverse functionalities, overcoming the inherent limitations of single atom catalysts (SACs). In this study, density functional theory calculations were conducted to investigate the reactivity of the carbon dioxide (CO2) reduction reaction (CO2RR) on metal sites of both DACs and SACs, as well as their synergistic effects on activity and selectivity. Calculation of the Gibbs free energies of CO2RR and associated values of the limiting potentials to generate C1 products showed that Cu acts as a promoter rather than an active catalytic centre in the catalytic CO2 conversion on heteronuclear DACs (CuN4-MN4), improving the catalytic activity on the other metal compared to the related SAC MN4. Cu enhances the initial reduction of CO2 by promoting orbital hybridization between the key intermediate *COOH 2p-orbitals and the metals 3d-orbitals around the Fermi level. This degree of hybridization in the DACs CuN4-MN4 decreases from Fe to Co, Ni, and Zn. Our work demonstrates how Cu regulates the CO2RR performance of heteronuclear DACs, offering an effective approach to designing practical, stable, and high-performing diatomic catalysts for CO2 electroreduction.