Atomically Paired Cu–Co Dual Sites for Near-Unity Ammonia Selectivity in Nitrate Electroreduction

Electrochemical nitrate-to-ammonia conversion enables sustainable, decentralized ammonia synthesis and environmental remediation. However, industrial-current-density ammonia selectivity requires atomic-level coupled catalytic sites to resolve the multistep proton-coupled electron transfer kinetics. Herein, we report an interpenetrating polymer network to atomically integrate immiscible Cu and Co dual sites. The network architecture combines a nonconjugated poly(styrenesulfonate) copolymer with a conjugated poly(3,4-ethylenedioxythiophene) network, interconnected by a polypyrrole molecular bridge by electrostatic and π-π stacking interactions. The design homogenizes charge distribution, enabling spatially precise codeposition of Cu-Co dual sites. The resulting adjacent Cu-Co dual sites accelerate intermediate hydrogenation, achieving 99% ammonia Faradaic efficiency at 3.5 A cm^-2 in a two-electrode flow cell (20 °C) with 200-h stability. Under industrial conditions (60 °C, 1.6 V), the system achieves 7.3 A cm^-2 current densities for simultaneous ammonia and oxygen production. Operando studies confirm that atomic Cu-Co proximity effectively addresses the kinetic barriers in the ammonia formation pathway. Our results bridge molecular-level catalyst design with industrial-level electrocatalysis, demonstrating the viability of dual-active-site engineering for high-throughput ammonia electrosynthesis.