Synthesis and application of a novel CuO-NiO-based electrode for electrocatalytic urea oxidation and hydrogen production

ABSTRACT

Graphical abstract showing carbon cloth electrodes modified with Cu-Ni mixed metal oxide catalysts prepared by combustion synthesis and hydrothermal methods, followed by electrolysis in alkaline urea solution at 1.5 V for hydrogen generation and urea degradation. A bar chart compares the two electrodes, showing cell voltage at 10 mA cm⁻2 (1.66 and 1.51 V), urea degradation efficiency (56.3 % and 29.74%), and H₂ production (3.39 and 1.4 mmol).

Urea electrolysis with Nickel catalysts has great potential in advancing sustainable hydrogen production and wastewater remediation. Here, we compare two synthesis methods – solution combustion (SC-CuNi/CC) and hydrothermal (HT-CuNi/CC) for fabricating Copper–Nickel mixed oxide catalyst-based carbon cloth electrodes for the integrated treatment of urea-rich wastewater and hydrogen generation. Despite both catalysts containing Ni and Cu as the active components, the solution combustion and hydrothermal methods result in different elemental compositions and phase structures, leading to distinct electrocatalytic performances. The HT-CuNi/CC exhibited superior performance over SC-CuNi/CC with a lower potential of 1.5 V at 10 mA cm−2, 89.67% urea degradation, and production of 3.39 mmol of hydrogen in 24 h. The enhanced activity is attributed to the intrinsic differences in the crystallinity, larger electrochemically active surface area, and a lower charge transfer resistance of the HT-CuNi/CC electrode. The synthesized HT-CuNi/CC electrodes serve as a promising, cost-effective, durable material for the treatment of urea-rich wastewater with hydrogen generation.