Ball-milled Ni@Mo₂C/C nanocomposites as efficient electrocatalysts for urea oxidation

Urea oxidation reaction (UOR) has been identified as a promising method for hydrogen production and the remediation of urea-rich wastewater by electrochemical techniques. In the present work, Ni/C and Ni@Mo₂C(x)/C electrocatalysts (x = 0.1, 0.2, 0.4, and 0.6 mol fraction of Mo₂C in Ni@Mo₂C) are prepared by ball milling method followed by annealing at 800 °C for 2 h under nitrogen atmosphere. Electrooxidation of urea is carried out using these electrocatalysts in an alkaline solution. Among them, the Ni@Mo₂C(0.4)/C catalyst shows a maximum current density of 96.5 mA cm^-2 at 1.7 V (versus RHE) in 1 M KOH and 0.33 M urea electrolyte. The Ni@Mo₂C(0.4)/C catalyst exhibits better catalytic activity, low overpotential, and charge transfer resistance with extremely low Tafel slope compared to other compositions for UOR. The synergistic electronic effect between Ni and Mo₂C components is responsible for generating active sites and facilitating the catalytic activity of UOR. The Ni@Mo₂C(x)/C electrocatalysts are promising for treating urea-rich wastewaters and for use as a substitute for suppressing OER in water-splitting reactions.