Electrode Potential-Programmed Active-Site Ensembles Govern Electrocatalysis

Abstract Electrode potential is the fundamental control variable of electrocatalysis, yet its conceptual role remains largely confined to modulating the energetics of predefined active site. How potential governs catalytic function at dynamically reorganizing electrified interfaces remains unresolved. Here, we show that the electrode potential governs electrocatalysis by programming the statistical populations of active-site ensembles. Using nitrate electroreduction on Cu(111) as a representative high-coverage electrocatalytic reaction, we demonstrate that catalytic activity is an emergent ensemble property arising from the potential-driven redistribution of kinetically distinct local reactive environments rather than any single surface configuration. Peak activity arises from the potential-driven enrichment of minority mixed 2NO/2NH2 ensembles that disproportionately carry catalytic flux despite remaining thermodynamically subordinate. Furthermore, activation barriers across more than 150 elementary reactions are organized into reaction-class-specific linear relationships governed by a common electronic descriptor—the excess charge on reactive Cu atoms (ΔqCu)—identifying interfacial charge redistribution as the unifying electronic principle linking electrode potential, ensemble evolution, and catalytic kinetics. These findings extend the conventional description of surface coverage from an average site occupation to a potential-programmed statistical distribution of local reactive environments and establish active-site ensemble programming as a general framework for understanding dynamic electrocatalytic interfaces under operating conditions.