A Zn-modulated NiFeCoCuZn high-entropy alloy for efficient electrocatalytic nitrate reduction to ammonia.

Electrocatalytic nitrate reduction to ammonia offers a promising route for coupling nitrate-contaminated wastewater remediation with value-added ammonia production, yet efficient catalysts with high selectivity and stability remain difficult to develop. Herein, a Zn-modulated NiFeCoCuZn high-entropy alloy catalyst was constructed, with Zn-free NiFeCoCu as the control. Structural and compositional characterization confirmed the near-equimolar multicomponent nature of NiFeCoCuZn, while Zn incorporation altered the particle-stacking morphology and surface core-level electronic states of the NiFeCoCu matrix. XPS analysis reveals negative shifts in the Ni, Fe, Co, and Cu core-level binding energies together with clear Zn 2p signals, indicating Zn-associated local electronic perturbation and multimetallic coupling. Benefiting from this regulated high-entropy alloy environment, NiFeCoCuZn delivers an NH3 yield rate of approximately 151.9 mg h-1 mg_cat-1 and an NH3 faradaic efficiency of approximately 91.2% at -0.5 V vs. RHE, outperforming the NiFeCoCu control. Chronoamperometry, UV-vis colorimetry, and 1H NMR cross-validation further verify its nitrate-to-ammonia conversion capability. Auxiliary free-energy calculations suggest that Zn incorporation optimizes nitrate-intermediate adsorption, lowers the initial nitrate-activation energy barrier, and maintains manageable competition from the hydrogen-evolution pathway, thereby promoting selective ammonia production.