Anchoring Ni 3 S 2 /Cr(OH) 3 hybrid nanospheres on Ti 3 C 2 @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 Ti 3 C 2 adsorbed on it, Ni 3 S 2 /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 Ni 3 S 2 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 Ni 3 S 2 /Cr(OH) 3 -Ti 3 C 2 @NF provide ideas for the development of low-cost, high-efficiency UOR electrodes with industrial application prospects.