One-pot Synthesis of NiO/NiCr2O4 Nanostructure as an Efficient Catalyst for Urea Electro-oxidation in Alkaline Media

The development of exceptionally active and stable electrocatalysts for the urea oxidation reaction (UOR) is a current research topic of interest. In this work, NiO/NiCr2O4 nanocomposites with different CrNi ratios (denoted as NiO/NiCr2O4-m, m = 1, 2, 3) were synthesized by a facile one-pot hydrothermal mothed without any template followed by a thermal treatment in N2 at 600 °C. The NiO/NiCr2O4-2 catalyst exhibited a large electrochemical surface area, which provided numerous accessible active sites and electronic transmission channels for the UOR. At a low catalyst loading of 50 μg cm–2, NiO/NiCr2O4-2 electrode delivered a current density of 994 mA cm−2 mg−1 (49.7 mA cm−2) in an electrolyte of 1.0 M KOH with 0.33 M urea at the potential of +0.5 V vs Ag/AgCl. The catalyst showed excellent redox characteristics and better stability compared to catalysts with other ratios of NiO/NiCr2O4, pure NiO and NiCr2O4 prepared similarly. Benefiting from the synergistic effect of NiO and NiCr2O4, multicomponent catalysts, particularly NiO/NiCr2O4-2, have demonstrated excellent electrocatalytic activities and are considered as promising candidates for direct urea fuel cells.