The Ni–P dual vacancies crystalline/amorphous bifunctional electrode with ZnO “electron pump” for urea-assisted electrolysis of water to produce hydrogen

Electrochemical urea electrolysis holds great potential for energy-efficient hydrogen production and wastewater treatment. However, developing cost-effective and highly active catalysts remains a challenge. In this study, a novel bifunctional electrocatalyst of Ni–Zn bimetallic nanosheets (ZnO–Ni2P) was synthesized on Ni foam (NF) for efficient urea decomposition in urea-containing wastewater. The results showed that inactive ZnO phase acted as an "electron pump", which facilitated electron redistribution between Ni and P atoms and created localized vacancies of Ni and P cations. This optimized electronic configuration enhanced the kinetics of both the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). Additionally, a unique particle-porous structure with abundant grain boundaries was achieved through the utilization of the Kirkendall Effect and Ostwald Ripening. In an alkaline urea electrolysis system, the alkaline urea electrolyzer assembled with ZnO–Ni2P/NF sample as both electrodes exhibited a low driving potential of only 1.424 V to achieve a current density of 10 mA cm−2, which outperformed the commercial noble metal-based electrolyzer (RuO2||Pt/C). The results verify that incorporating an inactive phase to manipulate the electronic structure of the active phase can be an effective strategy in developing catalysts for urea electrolysis.