Active Hydrogen Enrichment on Cu ₆ Sn ₅ ‐type High Entropy Intermetallics for Efficient Nitrate Reduction Reaction

Abstract Electrocatalytic nitrate reduction reaction (NO ₃ RR) provides a feasible strategy for green ammonia production and the treatment of nitrate pollution in wastewater. The generation of active hydrogen (H*) plays an important role in improving the selectivity, yield rate, and Faradaic efficiency of ammonia products. Here, structurally ordered nanoporous Cu ₆ Sn ₅ ‐type high entropy intermetallics (HEI) with extremely superior performance toward NO ₃ RR is demonstrated. The optimal nanoporous (Cu _0.25 Ni _0.25 Fe _0.25 Co _0.25 ) ₆ Sn ₅ HEI delivers a high NH ₃ Faradaic efficiency of 97.09 ± 1.15% and excellent stability of 120 h at the industrial level current density of 1 A cm ⁻² , accordingly directly converting NO ₃ ^‒ to high‐purity (NH ₄ ) ₂ HPO ₄ with near‐unity efficiency. Theoretical calculations combined with experimental results reveal that the ordered multi‐site nature of the nanoporous HEI can simultaneously promote water dissociation, reduce the reaction‐free energy of the hydrogenation process, and suppress hydrogen evolution. This work provides the design of the precious‐metal‐free HEI for sustainable NH ₃ synthesis and paves insights into the H* enrichment mechanism.