Hydrogen shuttle relay via Ru-Cu dual sites for high-efficiency nitrate electroreduction to green ammonia

The electrocatalytic nitrate reduction reaction (NO₃^-RR) offers a promising pathway for green ammonia synthesis, yet suffers from inefficient hydrogen utilization due to competing proton consumption pathways. Here, we engineer a Ru-Cu₂O/Cu catalyst via cationic spatial confinement, where Ru incorporation induces a dynamic hydrogen shuttle relay between reaction active sites. In situ/operando characterization technologies and theoretical calculations reveal that Ru sites accelerate water dissociation kinetics, generating mobile H* species that shuttle between Ru and Cu₂O to synchronize dual reaction pathways: H*-mediated nitrate hydrogenation and electron-driven NH_x intermediate conversion. Crucially, this shuttle relay enables kinetic matching of H flux between NO₃^-RR and hydrogen evolution reaction, suppressing parasitic H₂ evolution while achieving a Faradaic efficiency (FE) of 95.68 % with an NH₃ yield rate of 0.82 mmol cm⁻² h⁻¹ at −0.2 V vs. RHE—1.65-fold higher than Cu₂O/Cu controls. In addition, the catalyst maintains initial activity after 50 cycles. This work promotes the multi-step electrochemical hydrogenation process in nitrate reduction to ammonia (NO₃^-RR) by constructing an efficient hydrogen transport path.