Dual-Atom Catalysis on Defective Graphene: CO ₂ Reduction to Ethanol at Oxygen-Bridged Binuclear Sites

Using density-functional theory (DFT), we systematically investigate oxygen-bridged (Cu, Ag, Ce) and nonbridged (Cu, Ag) dual-atom catalysts supported on defective graphene for electrochemical CO 2 -to-ethanol conversion. We identify a structurally robust, buckled ground state for the Cu–O–Cu model catalyst. Thermodynamic analysis reveals that oxygen bridging in these dual-metal configurations lowers the energy penalty for *COOH formation, thereby improving its competitiveness against the *HCOO-mediated pathway. Electronic-structure analysis attributes this reactivity trade-off to a redistribution of metal d -states and enhanced metal–C covalency induced by the oxygen bridge. Conversely, Nudged Elastic Band (NEB) calculations demonstrate that nonbridged structures facilitate more favorable C–C coupling. For the Cu–O–Cu catalyst, while the formate (*HCOO) and carboxyl (*COOH) pathways are proximally thermodynamically degenerate during the initial proton-coupled electron-transfer step, existing experimental evidence of efficient ethanol production suggests the *COOH route remains kinetically operative. Furthermore, Ag–O–Ag emerges as a predictive target with favorable carboxyl-pathway energetics, despite a thermodynamic preference for formate. The Ce–O–Ce site, while the most strongly anchored of the catalysts studied (reflecting Ce’s high oxophilicity), is precluded for direct CO 2 activation by a prohibitively endergonic *COOH formation step. The nonbridged Ag–Ag and Cu–Cu catalysts suffer from a prohibitive *COOH formation step that prevents direct CO 2 activation. Nevertheless, owing to their superior C–C coupling kinetics, these nonbridged sites may still drive ethanol formation when *CO is supplied, e.g., via spillover from neighboring single-atom sites.