Atomic hydrogen pump boosts nitrite-to-ammonia conversion on Cu-Pd catalytic pairs over a wide potential range

Electrocatalytic NO₂‾-to-NH₃ reduction holds great promise for upcycling nitrogenous wastes to green ammonia. However, high NH₃ selectivity under applied potential windows remains a challenge due to the mismatch of potential-dependent *H supply and sluggish hydrogenation kinetics of *NO₂ on homogeneous catalytic sites. Herein, we constructed Cu-Pd catalytic pairs by integrating atomically dispersed Pd atoms into Cu matrix, in which the reactive *H adsorbed on the more hydrogenophilic Pd sites serves as atomic hydrogen pumps to enable hydrogenation of *NO₂ on adjacent Cu sites and prevent *H self-coupling, whereas pure Cu catalyst suffers severe hydrogen evolution under high overpotentials. The paired CuPd catalyst shows Faradaic efficiencies of NH₃ (FE_NH3) over 91 % from −0.3 to −0.9 V vs. RHE with a yield of 689.01 μmol h⁻¹ mg_cat.⁻¹ at −0.9 V in the neutral electrolyte, significantly outperforming most reported catalysts in applied potential windows. The Ni, Fe, and Ru atoms with high adsorption ability of *H could also improve the FE_NH3 of Cu, which not only proves the efficiency of the proposed atomic-hydrogen-pump strategy, but also provides a potential active-site design principle for multi-intermediate catalysis.