Lattice hydrogen-mediated dual-hydrogen synergy for efficient nitrate reduction reaction

• By employing lattice hydrogen (H lat ) as an additional efficient hydrogen source, we achieve both a stable supply of reactive hydrogen species and effective suppression of the competitive hydrogen evolution reaction (HER). • A unique dynamic H lat consumption-regeneration balance is established, which referred to as ‘hydrogen pump’ mechanism. • H lat operates synergistically with adsorbed hydrogen (H ads ) to establish a dual-hydrogenation pathway in nitrate reduction reaction (NO 3 - RR), significantly accelerating the reaction kinetics and suppressing HER. The electrocatalytic nitrate reduction reaction (NO 3 - RR) provides a sustainable route for mitigating aqueous nitrate pollution but suffers from insufficient hydrogen source and competitive hydrogen evolution reaction (HER). To address this, we constructed metal hydride electrocatalysts where lattice hydrogen (H lat ) cooperates with adsorbed hydrogen (H ads ) to promote NO 3 - RR. Computational studies revealed that at the active sites, both H ads originating from interfacial water dissociation and H lat adjacent to intermediates directly participate in NO 3 - RR, synergistically accelerating reaction kinetics. Notably, a unique ‘hydrogen pump’ mechanism is successfully established: H lat consumption during reaction generates vacancies, while at inactive sites, hydrogen species produced by spontaneous dissociation of interfacial water migrate spontaneously into the lattice, replenish vacancies, and regenerate H lat , which subsequently participate in further hydrogenation processes, thereby maintaining a dynamic balance of hydrogen cycle. Compared to pure metal catalysts, the metal hydrides system can utilize the dynamic synergy between H lat and H ads to significantly optimize the NO 3 - RR hydrogenation thermodynamics and kinetics, thus suppressing HER and boosting catalytic efficiency. Our work proposes a novel strategy employing a dual-hydrogenation pathway (H lat − H ads ) system that significantly enhances nitrate to ammonia conversion efficiency, enabling efficient removal of aqueous nitrate pollution and facilitating the recycling of nitrogen resources.