LAUSR

Abstract The sluggish kinetics of urea electro-oxidation seriously limits its application in hydrogen production and wastewater treatment. Herein, we demonstrated an easy freeze-drying/annealing approach induced phase structure tuning of graphene supported Ni-NiO nanoparticles system for efficiently boosting urea oxidation performance. The annealing temperature was found significant to influence the Ni precursors decomposition, crystal structure formation and catalytic performance for urea oxidation. By increasing the temperature from 350 °C to 550 °C, more metallic Ni was formed in the Ni-NiO system, and because of the efficient Ni-NiO synergistic effect and conductivity improvement, the sample obtained at 450 °C exhibited the highest catalytic activity and stability for urea oxidation. Specifically, the current density at 0.5 V was 38.24 mA cm−2, about 5.6 and 30 times of the control sample of graphene supported NiO and Ni respectively. Efficient kinetics and rapid charge transfer-ability were also found for urea oxidation by a series of electro-kinetics analysis. The current work showed an easy way for Ni-based catalyst structure tuning with enhanced kinetics for urea oxidation, which is helpful for the sustainable utilization of urea molecular in electrochemical energy.