Active Hydrogen Enrichment on Cu6Sn5-type High Entropy Intermetallics for Efficient Nitrate Reduction Reaction

Abstract

Electrocatalytic nitrate reduction reaction (NO₃RR) 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 Cu₆Sn₅-type high entropy intermetallics (HEI) with extremely superior performance toward NO₃RR is demonstrated. The optimal nanoporous (Cu_0.25Ni_0.25Fe_0.25Co_0.25)₆Sn₅ HEI delivers a high NH₃ 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 NO₃^‒ to high-purity (NH₄)₂HPO₄ 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 NH₃ synthesis and paves insights into the H* enrichment mechanism.