Porous hetero-structured nickel oxide/nickel phosphide nanosheets as bifunctional electrocatalyst for hydrogen production via urea electrolysis.

Urea electrolysis is a promising hydrogen generation and urea-rich wastewaters treatment technology, which requires the development of highly active electrocatalysts. In this study, porous hetero-structured nanosheet electrocatalyst (NiO/Ni2P/NF), composed of crystalline NiO and Ni2P, is prepared via the in-situ acid etching and gas-phase phosphating method, and the obtained NiO/Ni2P/NF material is applied as efficient urea oxidation and hydrogen evolution catalyst for the overall splitting of urea-containing wastewaters. An electrolyzer containing NiO/Ni2P/NF||NiO/Ni2P/NF electrode pair in an alkaline urea aqueous solution requires a potential of just 1.457 V to reach a current density of 10 mA cm-2, lower than that of 1.490 V needed for a Pt/C/NF||RuO2/NF electrolyzer to operate under the same current density. The study demonstrates the synergistic effect between NiO/Ni2P nanosheets as well as their uniform pore structure formed by the Kirkendall effect, resulting in enhanced electrocatalytic performance in hydrogen production by urea electrolysis.