Ab Initio Studies of Electrocatalytic CO₂ Reduction for Small Cu Cluster Supported on Polar Substrates

Small Cu clusters are excellent candidates for the electrocatalytic reduction of carbon dioxide (CO₂RR), and their catalytic performance is expected to be significantly influenced by the interaction between the substrate and cluster. In this study, we systematically investigate the CO₂RR for a Cu₃ cluster anchored on Janus MoSX (X = Se, Te) substrates using density functional theory calculations. These substrates feature a broken vertical mirror symmetry, which generates spontaneous out-of-plane polarization and offers two distinct polar surfaces to support the Cu₃ cluster. Our findings reveal that the CO₂RR performance on the Cu₃ cluster is strongly influenced by the polarization direction and strength of the MoSX (X = Se, Te) substrates. Notably, the Cu₃ cluster supported on the S-terminated MoSTe surface (Cu₃(S)@MoSTe) demonstrates the highest CO₂RR activity, producing methane. These results underscore the pivotal role of substrate polarization in modulating the binding strength of reactants and reaction intermediates, thereby enhancing the CO₂RR efficiency.