Superhydrophilic Porous CoOOH Nano-Architecture with Abundant Oxygen Vacancies for Enhanced Urea Electrooxidation at Ampere-Level Current Densities

The conversion of urea-containing wastewater into clean hydrogen energy has gained increasing attention. However, challenges remain, particularly with sluggish catalytic kinetics and limited long-term stability of urea oxidation reaction (UOR). Herein, we report the loosely porous CoOOH nano-architecture (CoOOH LPNAs) with hydrophilic surface and abundant oxygen vacancies (Ov) on carbon fiber paper (CFP) by electrochemical reconstruction of the CoP nanoneedles precursor. The resulting three-dimensional electrode exhibited an impressively low potential of 1.38 V at 1000 mA·cm−2 and excellent durability for UOR. Furthermore, when tested in an anion exchange membrane (AEM) electrolyzer, it required only 1.53 V at 1000 mA·cm−2 for industrial urea-assisted water splitting and operated stably for 100 h without degradation. Experimental and theoretical investigations revealed that rich oxygen vacancies effectively modulate the electronic structure of the CoOOH while creating unique Co3-triangle sites with Co atoms close together. As a result, the adsorption and desorption processes of reactants and intermediates in UOR could be finely tuned, thereby significantly reducing thermodynamic barriers. Additionally, the superhydrophilic self-supported nanoarray structure facilitated rapid gas bubble release, improving the overall efficiency of the reaction and preventing potential catalyst detachment caused by bubble accumulation, thereby improving both catalytic activity and stability at high current densities.