Crystallization of NiCo MOF-74 on a Porous NiO Film as an Anode for the Urea/H₂O₂Fuel Cell

NiCo-MOF-74 crystallized directly on the surface of porous NiO (p-NiO) film using a solvothermal method is proposed as an effective electrocatalyst for the anode in direct urea fuel cells. A nickel-to-cobalt ratio of 4:1 was found to show optimum catalytic activity toward urea oxidation with significant current enhancement in comparison to other electrodes, including Ni foil and p-NiO. At optimized conditions in an electrolyte solution of 3.0 M KOH and 1.0 M urea, a current density of around 110 mA cm-2 with a maximum power density of 4131 μW cm-2 can be produced. This is ascribed to the increase of the active surface area over conventional nickel-based anodes, providing an abundance of active sites for urea oxidation. Excellent stability and reproducibility over 15 h application in a direct urea fuel cell was obtained with cell voltage of ∼0.6 V. Powder X-ray diffraction shows the crystalline MOF film remains intact after chronoamperometry tests, and after fuel cell application, illustrating applicability in real devices.