Donor-acceptor Engineering in Ca-doped NiOOH as a Stable Electrocatalyst for Urea Oxidation Reaction

The thermodynamic barrier of the anodic oxygen evolution reaction in water electrolysis for green hydrogen production is high, significantly increasing energy consumption and hydrogen production costs. Replacing oxygen evolution reaction with the urea oxidation reaction can substantially reduce the voltage, offering advantages in energy efficiency and cost. However, catalysts for urea oxidation face challenges of declining activity during prolonged operation, which severely limits catalyst lifespan and hinders the industrial application of urea oxidation reaction as an alternative to oxygen evolution reaction. Here we show that a calcium-doping strategy enabling spontaneous electron transfer to nickel atoms effectively circumvents catalyst deactivation induced by over-oxidation. This electron-buffering mechanism, confirmed through Xray Photoelectron Spectroscopy binding energy shifts and stability tests, sustains active Ni³⁺ sites during prolonged urea oxidation operation. Density functional theory calculations elucidate the catalytic activity enhancement mechanism driven by calcium doping, revealing fundamental electronic and energetic modifications at the atomic scale. The catalyst Ca-NiOOH achieves a current density of 100 mA cm⁻² at 1.46 V for 400 hours without significant decay. Our research significantly enhances the longevity of catalysts for urea oxidation reaction.