Cobalt Incorporation Promotes CO<sub>2</sub> Desorption\nfrom Nickel Active Sites Encapsulated by Nitrogen-Doped Carbon Nanotubes\nin Urea-Assisted Water Electrolysis

The\npotential application prospects of urea-assisted water electrolysis\ntoward hydrogen production in renewable energy infrastructure can\neffectively alleviate energy shortages and environmental pollution\ncaused by rich urea wastewater. It is of prominent significance that\nadjusting the CO<sub>2</sub> desorption of nickel-based electrocatalysts\ncan overcome the slow reaction kinetics for urea oxidation reaction\n(UOR) to achieve exceptional catalytic activity. In this work, cobalt\n(Co) metal doping is employed to boost the UOR performance of nitrogen-doped\ncarbon nanotubes encapsulating nickel nanoparticle electrocatalysts\n(Ni@N-CNT). The influence of diverse Co doping concentrations on the\nperformance of UOR and hydrogen evolution reaction (HER) catalytic\nactivities associated with stability are systematically investigated.\nThe Co dopant can effectively promote the dynamical conversion of\nNi to Ni<sup>3+</sup> species; as a result, the UOR catalytic activity\nis improved by 1.8-fold at 1.6 V vs RHE. The DFT calculation results\nshow that the CoNi bimetallic structure possesses a comparably lower\nbinding energy for CO<sub>2</sub> adsorption accelerating the rate-limiting\nstep. Meanwhile, the Co dopant also boosts the HER performance, achieving\na 57 mV reduction in overpotential at 100 mA cm<sup>–2</sup> due to the creation of more active sites. In addition, the assembled\nurea-assisted water electrolysis attains 10 mA cm<sup>–2</sup> at merely 1.51 V as well as excellent stability.