Heterojunction-Induced Rapid Transformation of Ni 3+ /Ni 2+ Sites which Mediates Urea Oxidation for Energy-Efficient Hydrogen Production

Water electrolysis is an environmentally-friendly strategy for hydrogen production but suffers from significant energy consumption. Substituting urea oxidation reaction (UOR) with lower theoretical voltage for water oxidation reaction adopting nickel-based electrocatalysts engenders reduced energy consumption for hydrogen production. The main obstacle remains strong interaction between accumulated Ni and *COO in the conventional Ni -catalyzing pathway. Herein, a novel Ni /Ni mediated pathway for UOR via constructing a heterojunction of nickel metaphosphate and nickel telluride (Ni P O /NiTe), which efficiently lowers the energy barrier of UOR and avoids the accumulation of Ni and excessive adsorption of *COO on the electrocatalysts, is developed. As a result, Ni P O /NiTe demonstrates an exceptionally low potential of 1.313 V to achieve a current density of 10 mA cm toward efficient urea oxidation reaction while simultaneously showcases an overpotential of merely 24 mV at 10 mA cm for hydrogen evolution reaction. Constructing urea electrolysis electrolyzer using Ni P O /NiTe at both sides attains 100 mA cm at a low cell voltage of 1.475 V along with excellent stability over 500 h accompanied with nearly 100% Faradic efficiency.