Deciphering the origin of the advanced urea oxidation performance of nickel-based catalysts

Intermediate-valence Ni–O species are implicated in nickel-catalyzed urea oxidation but may continuously evolve toward more highly oxidized Ni–O states at elevated potentials, complicating mechanistic assignment and compromising reaction selectivity. We report a dynamically modulated strategy to construct a unique d–p interface (–O–Ni–N≡C–) between Prussian blue and LDH. DFT calculations and in situ characterizations indicate that proton/electron transfer from urea, together with the redox-responsive interfacial charge-buffering behavior of the –N≡C– units, maintains an intermediate Ni–O coordination/oxidation-state regime associated with Ni(OH)O-related species while suppressing further overoxidation toward NiOO-related states. This regulated Ni–O environment enables t-NFPBA@LDH to deliver high urea oxidation reaction (UOR) activity while significantly suppressing the formation of CNO - by-products. The catalyst demonstrates immense potential for urea fuel cells and wastewater degradation. This stabilization strategy offers a new paradigm for designing high-performance UOR catalysts.