Remarkable roles of electron-rich Mo and electron-deficient Ni active pairs in MoN/Ni heterostructures in promoting efficient urea oxidation reaction
The urea oxidation reaction (UOR) offers a low-energy pathway for hydrogen production via water electrolysis, but Ni-based catalysts suffer from Ni self-oxidation reaction (NSOR) that wastes energy and poisons active sites via strong CO2 adsorption. Here, we design MoN/Ni heterostructures to optimize the electronic structure of Ni sites, suppressing NSOR. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy confirm the formation of electron-rich Mo and electron-deficient Ni active pairs. In-situ spectroscopy, electrochemical tests, and density functional theory calculations reveal that electron-rich Mo sites enhance urea adsorption, while electron-deficient Ni sites prevent NSOR, facilitating urea activation, intermediate conversion, and CO2 desorption. The synergistic effect yields a current density of 100 mA cm−2 at only 1.39 V vs. RHE in 1 M KOH + 0.33 M urea, outperforming many NiOOH-based catalysts. This work introduces a novel high-performance catalyst with electron-rich/electron-deficient active pairs for efficient UOR.