Ni₃S₂/Ni Heterostructure Nanobelt Arrays as Bifunctional Catalysts for Urea-Rich Wastewater Degradation

Urea electrolysis is a cost-effective method for urea-rich wastewater degradation to achieve a pollution-free environment. In this work, the Ni3S2/Ni heterostructure nanobelt arrays supported on nickel foam (Ni3S2/Ni/NF) are synthesized for accelerating the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). It only needs ultralow potentials of 1.30 V and −54 mV to achieve the current density of ±10 mA cm–2 for UOR and HER, respectively. Meanwhile, the overall urea oxidation driven by Ni3S2/Ni/NF only needs 1.36 V to achieve 10 mA cm–2, and it can remain at 100 mA cm–2 for 60 h without obvious activity attenuation. The superior performance could be attributed to the heterostructure between Ni3S2 and Ni, which can promote electron transfer and form electron-poor Ni species to optimize urea decomposition and hydrogen production. Moreover, the nanobelt self-supported structure could expose abundant active sites. This work thus provides a feasible and cost-effective strategy for urea-rich wastewater degradation and hydrogen production.