Ag-supported single-atom metals for CO2 reduction: Atomistic insights into CO-binding moderation, scaling deviations,...

Electrochemical CO2 reduction to hydrocarbons requires catalysts that activate carbon-bound intermediates while suppressing the competing hydrogen evolution reaction (HER). Here, we use density functional theory to study single-metal adatoms on Ag(211). We identify two key effects. First, depositing intrinsically strong CO-binding metals (Ni, Co, and Fe) on Ag weakens CO adsorption relative to the pure metals, moving them toward a more favorable CO-binding regime for further reduction without surface poisoning. Second, early transition metals-especially Ti-behave differently: Ti maintains moderate CO binding but stabilizes CHO much more strongly, effectively decoupling CO and CHO adsorption and deviating from linear scaling relationships. As a result, the CO → CHO activation barrier drops from 1.23 eV on Cu/Ag, taken here as an experimental benchmark for hydrocarbon production, to 0.62 eV on Ti/Ag. Single adatoms bind hydrogen weakly and suppress HER, while larger clusters restore strong H binding and increase HER activity. Our work shows that deposited-metal identity and site size independently control CO activation and HER, providing simple design rules for CO2 reduction catalysts for hydrocarbon production.