Synergistic Cu-Co Bimetallic Catalysts for Electrocatalytic Nitrate Reduction to Ammonia: From Atomic-Level Design to Relay Catalysis.

Electrocatalytic nitrate reduction to ammonia (NH3) offers a green technology for converting nitrogenous water pollutants into value-added chemicals. Compared with single-metal counterparts, bimetallic copper-cobalt (Cu-Co) systems possess intrinsic atomic-level synergistic effects that simultaneously boost reactant adsorption and reaction kinetics, leading to superior electrocatalytic performance. This review systematically summarizes the relationship between structural design and catalytic activity in Cu-Co electrocatalysts, focusing on precise strategies for tuning active site spatial/electronic configurations through atomic-scale engineering, phase optimization, and morphological control. Central to this enhanced performance is a relay catalysis mechanism, where Cu sites efficiently adsorb nitrate while adjacent Co sites act as proton providers, markedly elevating NH3 yield rate, Faradaic efficiency, and selectivity. Finally, we highlight major challenges regarding commercialization-including active-phase identification via coupled in situ characterizations and theoretical calculations, design of poison-resistant and durable Cu-Co electrocatalysts, and reactor design-to bridge laboratory innovation and industrial deployment.