Rapid Reconstruction of Amorphous/Crystalline Heterojunction Boosts Nickel-Catalyzed Urea Electrooxidation

Electrochemical urea oxidation (UOR) represents an energy-efficient alternative to the oxygen evolution reaction for hydrogen production via water electrolysis. However, its implementation is hindered by sluggish kinetics and an elusive reaction mechanism. Here, we construct a nanoparticulate amorphous/crystalline Ni heterojunction encapsulated within graphene (A/C-Ni@G) via a facile thermal shock strategy. This heterojunction enables the rapid electrochemical reconstruction of Ni into vacancy-rich NiOOH, which serves as the active species to facilitate the C–N bond cleavage and reduce the energy barrier of the rate-determining step for the UOR, as evidenced by detailed in situ spectroscopic characterizations and theoretical calculations. Notably, A/C-Ni@G achieves the UOR performance with a low potential of 1.358 V at a current density of 100 mA cm–2 and a Tafel slope of 21.9 mV dec–1. This work provides fundamental insights into the reconstruction dynamics in heterojunction catalysts and establishes a design paradigm for efficient urea-based energy conversion.