Temperature effect on crystallinity and chemical states of nickel hydroxide as alternative superior catalyst for urea electrooxidation
Temperature effect on crystallinity and chemical states of nickel hydroxide as alternative superior catalyst for urea electrooxidation
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DOI：
10.1016/j.electacta.2019.01.150
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发表时间：
2019-04-01
影响因子：
6.6
通讯作者：
Yang, Xiulin
中科院分区：
文献类型：
--
作者：
Gan, Qiuping;Cheng, Xiaoyang;Yang, Xiulin
开发一种高效、稳定的催化剂是电化学尿素氧化的关键。在所有的物理参数中，反应温度对催化剂的性能起着关键的作用。在此，我们详细研究了温度对水热法合成氢氧化镍-碳纳米管复合材料的影响及其对尿素电氧化的催化性能。我们的研究表明，较高的温度提高了β-Ni（OH）（2）物种的结晶度。此外，Ni（OH）（2）-CNTs复合材料中Ni（III）物种随反应温度的变化存在一个最佳点，在80 ℃时，β-Ni（OH）（2）-CNTs中Ni（III）的含量最高。同时，电化学研究表明，优化的β-Ni（OH）（2）-CNT（80 ℃，95.6 m（2）g（-1））催化剂的电化学活性表面积（ESA）分别是在20 ℃和140 ℃下合成的β-Ni（OH）（2）-CNT的4.51倍和2.76倍。β-Ni（OH）（2）-CNT的较高ESA（80 ℃）还伴随着上级电化学尿素氧化，峰值电流密度为98.5 mA cm（-2），显著高于所有其他研究的催化剂。此外，最佳的β-Ni（OH）（2）-CNT（80 ℃）在不间断的长期运行后也表现出最高的初始和极限电流密度。β-Ni（OH）（2）-CNT（80 ℃）催化剂的这些优异性能表明Ni（III）含量的积极作用，其提供更多的催化活性物质沿着CNT的独特层状结构作为载体以促进电子/质量传递和气体排放。(C)2019爱思唯尔有限公司版权所有。
Developing a highly efficient and stable catalyst, composited by inexpensive, earth-abundant and nontoxic materials, is the critical issue for electrochemical urea oxidation. Among the all other physical parameters, the reaction temperature plays the key role in catalyst performance. Herein, we have studied the effect of temperatures on the synthesis of nickel hydroxide-carbon nanotubes composites via a facile hydrothermal method and the catalytic performance towards urea electro-oxidation in detail. Our studies indicate that the higher temperature enhances the crystallinity of beta-Ni(OH)(2) species. Furthermore, the Ni(III) species in Ni(OH)(2)-CNTs composites show an optimal point upon the changes of the reaction temperature, and the highest Ni(III) content appears at 80 degrees C of beta-Ni(OH)(2)-CNTs. Meanwhile, electrochemical studies show that the electrochemically active surface areas (ESA) of the optimized beta-Ni(OH)(2)-CNTs (80 degrees C, 95.6 m(2) g(-1)) catalyst is 4.51- and 2.76-fold higher than that of beta-Ni(OH)(2)-CNTs synthesized at 20 and 140 degrees C, respectively. The higher ESA of beta-Ni(OH)(2)-CNTs (80 degrees C) also accompanies a superior electrochemical urea oxidation with a peak current density of 98.5 mA cm(-2), significantly higher than all the other studied catalysts. Additionally, the optimal beta-Ni(OH)(2)-CNTs (80 degrees C) also demonstrates the highest initial and limiting current densities after uninterrupted long-term operation. These excellent performance of beta-Ni(OH)(2)-CNTs (80 degrees C) catalyst indicates the positive effect of Ni(III) content which provides more catalytically active species along with the unique lamellar structures of CNTs as the support to facilitate electron/mass transfer and gas emission. (C) 2019 Elsevier Ltd. All rights reserved.