Enriched and Sustained Oxygen Vacancies in Amorphous NiWO _x Enhance and Stabilize Urea Electrooxidation

Abstract

ABSTRACT Urea electrolysis is promising for energy‐saving hydrogen production and effective treatment of urea‐polluted water. However, the activity and stability of Ni‐based electrocatalysts for the anodic urea oxidation reaction (UOR) are limited by the lack of active NiOOH and strong intermediates adsorption. Although oxygen vacancies (O v ) benefit for the UOR, continuous generation and stabilization of O v remain challenges. Herein, we propose an “amorphous oxygen mechanism (AOM)” for urea electrooxidation in amorphous nickel tungsten oxide (NiWO x ) with tunable O v concentrations. Systematic experimental and theoretical studies demonstrate that enriched O v, not only facilitate the formation of active NiOOH species, but also significantly reduce the energy barrier of the rate‐determining step. More importantly, the amorphous state allows more defects, which enables the in situ regeneration and sustainability of O v during the UOR via a continuous oxygen escape in the amorphous catalyst. Notably, NiWO x with the highest O v achieves an ultralow potential of 1.34 V at 10 mA cm −2 with incredible 400 h stability. Moreover, only 1.46 V is demanded for urea electrolysis with 100 mA cm −2 in an anion‐exchange membrane electrolyzer. The long‐term stability is also impressive. This work highlights the significant role of amorphous structure, providing valuable insights into catalyst design in electrocatalysis.