Self‐supporting Nickel Phosphide/ Hydroxides Hybrid Nanosheet Array as Superior Bifunctional Electrode for Urea‐Assisted Hydrogen Production

Abstract Urea oxidation reaction (UOR) is an important strategy to synergistically realize energy‐saving hydrogen evolution reaction (HER) and urea‐rich wastewater purification by replacing water oxidation in water electrolysis. However, the efficient realization of integral urea electrolysis remains challenging. Herein, a self‐supporting Ni 2 P−Ni(OH) 2 hybrid nanosheet array on nickel foam (Ni 2 P@Ni(OH) 2 /NF) is designed by a simple hydrothermal accompanied by electrodeposition strategy, representing a new class of bifunctional electrodes for urea‐assisted water electrolysis. The Ni 2 P@Ni(OH) 2 /NF reaches the current density of 100 mA cm −2 at potentials of −0.16 V and 1.388 V, along with small Tafel slopes of 69 mV dec −1 and 33 mV dec −1 for HER/UOR, respectively. For the HER||UOR coupled system, the constructed electrolyzer only needs 1.38 V to realize the current density of 100 mA cm −2 under 80 °C. The superior bifunctional activity of the Ni 2 P@Ni(OH) 2 /NF electrode is ascribed to the combined merits of the Ni 2 P@Ni(OH) 2 heterostructure, enriching the catalytic active sites and offering a faster charge transfer process for electrolysis. Our work provides important insights into the design of highly active bifunctional catalysts from the perspective of overall water electrolysis.