Achieving low-energy consumption water-to-hydrogen conversion via urea electrolysis over a bifunctional electrode of hierarchical cuprous sulfide@nickel selenide nanoarrays.

Abstract Replacing sluggish oxygen evolution reaction with thermodynamically favorable urea oxidation reaction is a promising strategy for hydrogen-generation from water with low-energy consumption. However, the involved six-electron transfer process makes it formidable and seems critical. Hence, exploring high-efficient and low-cost bifunctional catalysts toward urea electrolysis is highly desirable. Herein, hierarchical cuprous sulfide@nickel selenide nanowire arrays were grown on copper foam (termed as Cu2S@Ni3Se2) via a developed method composed of in situ chemical deposition, ion exchange and electrodeposition. The as-prepared bifunctional Cu2S@Ni3Se2 not only shows remarkable hydrogen evolution reaction (HER) activity but also affords excellent urea oxidation reaction (UOR) activity. A subsequently configured Cu2S@Ni3Se2 // Cu2S@Ni3Se2 full-cell (Cu2S@Ni3Se2 working as both anode and cathode) only requires a low voltage of 1.48 V to launch a current density of 10 mA cm-2, not only surpassing the routine water electrolysis (1.70 V), but also outperforming the state-of-the-art Pt/C // IrO2 for urea electrolysis (1.65 V). Moreover, the performance is superior to most recently reported ones that configured with other catalysts. This work presents a solid step for hydrogen-generation from water with low-energy consumption.