Abstract
Development of high-efficient and stable electrocatalysts for urea oxidation reaction (UOR) is of a great challenge due to the sluggish kinetics of 6e− transfer process. Here, we have developed a facile and easy-to-scale approach to fabricate two-dimensional Ni(III)-rich Ni(OH)2 nanosheets on amine-functionalized carbon (Ni3+-rich Ni(OH)2/C-NH2). Morphological characterizations confirm the existence of nanosheets, and XPS spectra indicate that the content of Ni3+ species in Ni3+-rich Ni(OH)2/C-NH2 (ca. 57.6%) is significantly higher than that of in Ni(OH)2/C-NH2 (ca. 43.1%) and Ni(OH)2/C (ca. 20.7%). Electrochemical analyses illustrate that the as-prepared Ni3+-rich Ni(OH)2/C-NH2 catalyst exhibits the highest current density (91.72 mA cm−2) at a potential of 0.61 V, which is 2.06-, 2.08- and 3.47-fold higher than that of Ni(OH)2/C-NH2, Ni(OH)2/C and Pt/C, respectively. Moreover, the Ni3+-rich Ni(OH)2/C-NH2 catalyst also demonstrates an outstanding voltammetric cycles and long-term chronoamperometric stability. The superior electrocatalytic activity and stability could be ascribed to the synergistic effect of Ni3+ doping as well as the amine-functionalized carbon, where higher concentration Ni3+ species in Ni(OH)2 sheets could provide more active sites for adsorption and transformation of urea molecules, while fluffy C-NH2 support could enhance the ability of solute diffusion, electron transport and gas emissions, thereby dramatically improve the catalytic activity.
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•Two-dimensional Ni3+-rich β-Ni(OH)2 nanosheets on amine functionalized carbon was synthesized by a facile ammonia-assisted evaporating method.•The developed Ni3+-rich Ni(OH)2/C-NH2 catalyst exhibits the highest catalytic activity and stability compared to other catalysts reported for urea electro-oxidation.•The synergistic effect of Ni3+ species doping in β phase of 2D Ni(OH)2 nanosheets and amine functionalized carbon dominate the superior catalytic performance.