Iron‑molybdenum-based nitrides with nanorod heterostructure as multifunctional electrocatalysts for urea oxidation...

This work aims to develop multifunctional electrocatalysts capable of efficiently facilitating the concurrent oxygen evolution reaction (OER), urea oxidation reaction (UOR), and hydrogen evolution reaction (HER) at high current densities, representing a key step toward a dual-purpose technology for clean hydrogen production and urea-rich wastewater treatment. To achieve this goal, a flower-like Fe₃N-MoN heterostructure electrocatalyst composed of nanorods was synthesized on nickel foam (NF) using a hydrothermal-nitridation approach. This electrocatalyst exhibited exceptional multifunctional activities for OER (overpotential: η_10,1000 = 206, 374 mV), UOR (potential: E_10,500 = 1.35, 1.49 V), and HER (η₁₀₀₀ = 445 mV), while maintaining remarkable stability for over 48 h at 500 mA cm^-2. When employed in a two-electrode system (Fe₃N-MoN/NF (+) || Fe₃N-MoN/NF (-)), the catalyst demonstrated low operating potentials for overall water electrolysis (E_10,500 = 1.54, 1.78 V). Notably, the urea-assisted electrolysis system required a significantly lower voltage, achieving E₁₀ = 1.33 V. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicate that the enhanced catalytic ability should be stemmed from electronic structure optimization and surface reconstruction of Fe₃N-MoN heterostructure. This work demonstrates a rational design method for high-efficiency multifunctional electrocatalysts that couple low-energy hydrogen production with electrolytic purification of urea-rich wastewater.