Anchoring Ni₃S₂/Cr(OH)₃ hybrid nanospheres on Ti₃C₂@NF dual substrates by ion exchange for efficient urea electrolysis

Developing efficient nonprecious-metal urea oxidation reaction (UOR) electrocatalysts will promote large-scale hydrogen production via electrolytic water splitting. Therefore, on dual substrates consisting of nickel foam (NF) with high-conductivity Ti₃C₂ adsorbed on it, Ni₃S₂/Cr(OH)₃ nanosphere catalysts were facilely in situ constructed at room temperature via an ion-exchange method. The optimized electrode exhibits obvious advantages and excellent stability in a solution of 1 M KOH containing 0.5 M urea, with an overpotential of 130 mV at 10 mA cm⁻² for the UOR. The two-electrode system requires merely 1.52 V to attain a current density of 10 mA cm⁻², and shows excellent durability over 60 h. The superior performance of the electrode is mainly attributed to the following three aspects: (i) the introduction of amorphous Cr(OH)₃, which improves the catalyst morphology and regulates the electronic structure of the active metal; (ii) the synergistic catalysis by the defect-rich Ni₃S₂ and Cr(OH)₃ on the nanospheres; (iii) the large adsorption surface and excellent electrical conductivity provided by the dual substrates; and (iv) the mild preparation process, which provides excellent stability for the electrode. The ingenious structural design and simple preparation method of Ni₃S₂/Cr(OH)₃-Ti₃C₂@NF provide ideas for the development of low-cost, high-efficiency UOR electrodes with industrial application prospects.