<i>In Situ</i> Growth of Porous Ultrathin Ni(OH)<sub>2</sub> Nanostructures on Nickel Foam: An Efficient and Durable Catalysts for Urea Electrolysis
Liaoyuan Xia, Yu Liao, Yan Qing, Han Xu, Zhifei Gao, Wanqian Li, Yiqiang Wu
Abstract
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.