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.

中文翻译：

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具有高镍 (III) 物种含量的二维氢氧化镍纳米片可实现优异的尿素电氧化

摘要 由于 6e− 转移过程的动力学缓慢，开发用于尿素氧化反应 (UOR) 的高效稳定电催化剂是一个巨大的挑战。在这里，我们开发了一种简便且易于扩展的方法来在胺功能化碳（富含 Ni3+ 的 Ni(OH)2/C-NH2）上制造二维富含 Ni(III) 的 Ni(OH)2 纳米片. 形态表征证实了纳米片的存在，XPS 光谱表明富含 Ni3+ 的 Ni(OH)2/C-NH2（约 57.6%）中 Ni3+ 物种的含量显着高于 Ni(OH)2/ C-NH2（约 43.1%）和 Ni(OH)2/C（约 20.7%）。电化学分析表明，所制备的富含 Ni3+ 的 Ni(OH)2/C-NH2 催化剂在 0.61 V 的电位下表现出最高的电流密度 (91.72 mA cm-2)，分别为 2.06-、2.08- 和 3.47-比 Ni(OH)2/C-NH2 高一倍，分别为 Ni(OH)2/C 和 Pt/C。此外，富含 Ni3+ 的 Ni(OH)2/C-NH2 催化剂还表现出出色的伏安循环和长期计时电流稳定性。优异的电催化活性和稳定性可归因于 Ni3+ 掺杂和胺功能化碳的协同作用，其中 Ni(OH)2 片中较高浓度的 Ni3+ 物种可以为尿素分子的吸附和转化提供更多的活性位点，而蓬松的C-NH2载体可以增强溶质扩散、电子传输和气体排放的能力，从而显着提高催化活性。