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

Graphical Urea-Assisted Hydrogen Production : A kind of self-supporting Ni 2 P−Ni(OH) 2 hybrid nanosheet arrays is exploited as highly-active bifunctional electrode for urea-assisted hydrogen production in alkaline medium, which put forward a simple strategy to design novel hybrid structure for energy-saving hydrogen production. 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.