In Situ Growth of Porous Ultrathin Ni(OH)₂ Nanostructures on Nickel Foam: An Efficient and Durable Catalysts for Urea Electrolysis

Urea electrolysis is a potential energy-efficient hydrogen (H₂) production method that can simultaneously purify urea-rich wastewater. However, the lack of inexpensive and effective electrocatalysts for the urea oxidation reaction (UOR) hampers its widespread use. Herein, hierarchically porous and ultrathin Ni­(OH)₂ nanostructures in situ grown onto nickel foam (Ni­(OH)₂@NF) are developed as efficient and durable electrocatalysts for UOR via a simple and cost-effective ultrasonic/heating-assisted activation strategy. The ultrathin Ni­(OH)₂ nanostructures comprise highly active surfaces and rapid diffusion pathways for active species; meanwhile, the excellent electrical conductivity of the NF skeletons effectively improves the charge transfer of the catalyst. Consequently, this Ni­(OH)₂@NF electrode exhibits excellent urea catalytic activity (low oxidation potential of ∼1.35 V at 10 mA cm^–2) and has remarkable operational stability (potential increase by only 0.22% after 40 h of durability testing) that is superior to most UOR catalysts. By employing the freestanding electrode as the anode and commercial Pt/C supported on NF as the cathode, this two-electrode urea electrolysis cell exhibited a current density of 50 mA cm^–2 at a low cell voltage (1.45 V, 250 mV below a urea-free counterpart) with a robust durability (>40 h). This work provides a valuable insight for designing scalable and high-performance UOR electrocatalysts, which are promising for utilization in energy-efficient H₂ production.