Intensifying Interfacial Reverse Hydrogen Spillover for Boosted Electrocatalytic Nitrate Reduction to Ammonia

Abstract Rational regulation of active hydrogen (*H) behavior is crucial for advancing electrocatalytic nitrate reduction reaction (NO 3 RR) to ammonia (NH 3 ), yet in‐depth understanding of the *H generation, transfer, and utilization remains ambiguous, and explorations for *H dynamic optimization are urgently needed. Herein we engineer a Ni 3 N nanosheet array intimately decorated with Cu nanoclusters (NF/Ni 3 N−Cu) for remarkably boosted NO 3 RR. From comprehensive experimental and theoretical investigations, the Ni 3 N moieties favors water dissociation to generate *H, and then *H can rapidly transfer to the Cu via unique reverse hydrogen spillover mediating interfacial Ni−N−Cu bridge bond, thus increasing *H coverage on the Cu site for subsequent deoxygenation/hydrogenation. More impressively, such intriguing reverse hydrogen spillover effect can be further strengthened via elegant engineering of the Ni 3 N/Cu heterointerface with more intimate contact. Consequently, the NF/Ni 3 N−Cu with Cu nanoclusters intimate anchoring presents record NH 3 yield rate of 1.19 mmol h −1 cm −2 and Faradaic efficiency of 98.7 % at −0.3 V vs. RHE, being on par with the state‐of‐the‐art ones. Additionally, with NF/Ni 3 N−Cu as the cathode, a high‐performing Zn−NO 3 − battery can be assembled. This contribution illuminates a novel pathway to optimize *H behavior via distinct reverse hydrogen spillover for promoted NO 3 RR and other hydrogenation reactions.