Crystalline–amorphous interfaces of NiO-CrO_x electrocatalysts for boosting the urea oxidation reaction

The overall energy efficiency of electrochemical systems is severely hindered by the traditional anodic oxygen evolution reaction (OER). Utilizing urea oxidation reaction (UOR) with lower thermodynamic potential to replace OER provides a promising strategy to enhance the energy efficiency. Amorphous and heterojunctions electrocatalysts have been aroused extensive studies owing to their unique physicochemical properties and outperformed activity. Herein, we report a simple method to construct a novel crystalline–amorphous NiO-CrO_x heterojunction grown on Ni foam for UOR electrocatalyst. The NiO-CrO_x electrocatalyst displays excellent UOR performance with an ultralow working potential of 1.32 V at 10 mA·cm⁻² and ultra-long stability about 5 days even at 100 mA·cm⁻². In-situ Raman analysis and temperature-programmed desorption (TPD) measurement verify that the presence of the amorphous CrO_x phase can boost the reconstruction from NiO to active NiOOH species and enhance adsorption ability of urea molecule. Besides, the unique crystalline–amorphous interfaces are also benefit to improving the UOR performance.