Ce2S3 induces the rapid conversion of Ni3S2 to highly active NiOOH phase of urea oxidation reaction.

The urea oxidation reaction (UOR) represents a promising alternative to the oxygen evolution reaction (OER) for energy-saving hydrogen production due to its lower thermodynamic energy consumption. However, the high formation potential and poor stability of NiOOH severely restrict the UOR kinetics of Ni-based catalysts. In this study, a heterostructure comprising electron-rich Ce2S3 and electron-deficient Ni3S2 was constructed to enhance the UOR kinetics. The electron-deficient Ni3S2 significantly lowers the oxidation energy barrier and facilitates the formation of the active NiOOH phase. Concurrently, the incorporation of Ce2S3 decreases the charge transfer resistance (Rct), promotes efficient electron transfer, and stabilizes the NiOOH phase. Furthermore, the synergy between the electron-rich and electron-deficient regions favors urea adsorption and dissociation. Benefiting from these merits, the Ni3S2/Ce2S3 catalyst exhibits outstanding UOR activity, requiring a potential of only 1.359 V to deliver 10 mA·cm-2 and maintaining stable operation for at least 130 h. To further evaluate its practical application potential, a two-electrode electrolyzer was assembled, achieving a current density of 10 mA·cm-2 at a voltage of 1.466 V with high stability for over 100 h. This work provides new insights into the design and construction of highly efficient and stable UOR electrodes.