Mechanistic Insights into Urea-Assisted NiCu Electrocatalysts for Enhanced Ammonia Electrolysis from Concentrated Wastewater

Urea is widely adopted in the synthesis of NiCu catalysts, yet its intrinsic regulatory mechanism during electrodeposition remains ambiguous. In this study, experiments combined with molecular dynamics (MD) simulations were used to uncover the modulation effect of urea on Ni/Cu electrodeposition for electrocatalytic NH₃ cracking toward H₂ production. Among the three tested urea concentrations (0, 5, and 10 mmol L⁻¹), 5 mmol L⁻¹ was identified as the optimal dosage. This optimal condition yielded the maximum current density (47.47 mA cm⁻²) and the largest electrochemically active surface area (243.33 cm²). The as-fabricated NiCu catalyst achieved an outstanding NH₃–N degradation efficiency of 91.44%, a nitrogen selectivity of 73.21%, a Faradaic efficiency of 53.57%, and a minimized energy consumption of 16.08 kW・h kg⁻¹. Combined electrode characterization and MD simulations revealed an explicit structure–performance relationship: urea retarded the migration of Ni²⁺ and Cu²⁺ and regulated their deposition kinetics, thereby enabling a uniform Ni–Cu elemental distribution. This study demonstrates that a moderate urea concentration is a feasible strategy to tailor NiCu deposition behavior, providing a rational guideline for the targeted design of high-efficiency alloy electrocatalysts.