NiFeCoRuW High-Entropy Alloy With W-Modulated Local Electronic Structure for Enhanced Electrocatalytic Nitrate Reduction to Ammonia.

Electrocatalytic nitrate reduction to ammonia provides a promising strategy for coupling nitrate-polluted wastewater remediation with distributed ammonia production, but achieving high performance with reasonable selectivity and stability remains challenging. Herein, a W-modulated NiFeCoRuW high-entropy alloy catalyst is prepared through microfluidic-assisted liquid-phase reduction followed by high-temperature alloying, with W-free NiFeCoRu as the control. Structural and surface analyses reveal that W incorporation modifies the diffraction features, particle-stacking morphology, and core-level electronic states of the NiFeCoRu matrix, indicating local structural distortion and multimetallic electronic coupling rather than simple compositional addition. Benefiting from the W-containing multimetallic environment and increased electrochemically accessible sites, NiFeCoRuW achieves an NH3 Faradaic efficiency of 98.1% and an NH3 yield rate of 162.65 mg h-1 mg_cat-1 at -0.5 V versus RHE, outperforming reported high-entropy-alloy-based NO3RR catalysts. UV-vis colorimetry and NMR cross-validation support reliable ammonia quantification. In situ DEMS trends and auxiliary free-energy profiles further suggest that W-assisted electronic reconstruction favors nitrate activation and promotes deep reduction involving *NOH/*N-related intermediates while limiting excessive hydrogen-evolution competition.