Surface engineering of hierarchical Ni(OH)2 nanosheet@nanowire configuration toward superior urea electrolysis

In order to resolve the pollution and waste caused by urea-rich wastewater, designing superior and stable earth-abundant catalysts for urea oxidation reaction (UOR) have always been attractive and urgent but still challenging. Herein, we report on a facile surface-engineering strategy of building hierarchical nickel hydroxide nanosheet@nanowire array on Ni foam (Ni(OH)2 NS@NW/Ni foam) as anode material toward superior urea electrolysis. This Ni(OH)2 based-catalyst with peculiar nanosheet@nanowire configuration just requires a small potential of 0.34 V (vs. SCE) to drive 10 mA cm−2 in 1.0 M KOH with 0.33 M urea, which outperforms the one with pure nanosheet array architecture and even the commercial Pt/C catalyst. Further, a two-electrode electrolysis system is built here with the cathode of cobalt phosphide nanowire array on Ni foam (Co2P NW/Ni foam) and anode of Ni(OH)2 NS@NW/Ni foam for overall urea electrolysis, which needs a low voltage of 1.58 V to drive 5 mA cm−2 in 1.0 M KOH with 0.33 M urea. Note that, the current density presented in this work is based on the real surface area of Ni foam but not the geometric area, unless otherwise specified.