Comprehensive Understanding of the Electrocatalytic Mechanism for Co/Fe/Cu Doped Ni(OH)<sub>2</sub> on Urea Oxidation Reactions: Theory and Experiment
Lu Chen, Wenjie Jiang, Jiayu Zhang, Bingxian Chu, Zhixiang Zhai, Tianqi Yu, Haixiang He, Shibin Yin
Abstract
α -Ni(OH) 2 is an efficient candidate for urea oxidation reaction (UOR) but its instability and high energy barriers restrict its application. The introduction of transition metals is a strategy to solve these problems, but systematic investigations of mechanisms are limited. Herein, a range of isoelectronic transition metals (ITMs) (M = Co, Fe, and Cu) doped Ni(OH) 2 catalysts on UOR are studied simultaneously in theory and experiment. By introducing Co and Fe into the lattice of Ni(OH) 2, electronic structure transfer is facilitated, resulting in effective promotion of the urea absorption and CO 2 desorption, and intrinsic activity can be increased. Among these catalysts, Co–Ni(OH) 2 with the lowest energy barrier (1.76 eV) for rate-determining steps might exhibit excellent activity. To verify the theoretical prediction, samples are synthesized via the one-step hydrothermal method. ITMs incorporation can stabilize the α phase of Ni(OH) 2, confirmed by chronopotentiometry and X-ray diffraction results. Agreeing with the calculation, Co–Ni(OH) 2 manifests superior UOR properties than other catalysts, providing the smallest onset potential (1.304 V vs RHE) and Tafel slope (24 mV dec –1 ). This study can provide a comprehensive understanding of the ITMs-Ni(OH) 2 catalytic on UOR mechanism, which could be instructive for designing UOR catalysts with higher activity.