基于碳纳米管的氧还原反应催化剂的研究

发布时间：2018-02-10 14:19

  本文关键词： 氧还原反应 电催化剂 碳纳米管 聚苯胺 三聚氰胺　出处：《重庆大学》2015年硕士论文　论文类型：学位论文

【摘要】：化石能源的消耗及其导致的污染问题,使得探索新的能源成为世界各国所面临的重要挑战。燃料电池因具有能量转换效率高、污染低等优势而备受青睐。作为燃料电池重要组成部分的空气电极,控制和影响电池性能高低的关键瓶颈,特别是空气电池中的ORR具有动力学迟缓及反应途径多样性的特点,导致电池很难大电流放电。寻找廉价易得高效的燃料电池阴极电催化剂来替代贵金属铂基催化剂是燃料电池发展的重要方向。本文选用廉价易得且高氮含量的聚苯胺、三聚氰胺来共同修饰碳纳米管制备TM-N/C型催化剂。同时优化催化剂的制备条件如热处理时间、热处理温度以及金属添加量等因素。实验利用线性伏安扫描对其电化学活性进行测试,采用旋转圆盘电极测试其催化机理及稳定性,根据时间-电流曲线测试其耐甲醇性能,用SEM、XRD、XPS对催化剂的形貌及结构进行表征测试。实验结果表明,双氮源共同修改碳纳米管比单一氮源修饰具有明显的优势,双氮源参杂碳纳米管在最优条件下所制备的N/C催化剂起始氧还原电位可以到-35 m V,峰电位可以达到-113 m V;过渡金属钴的添加能够提高催化剂的活性,Co-N/C-A与N/C相比其起始电位和峰电位分别正移5 m V和25 m V,且具有优异的耐甲醇性能;Co-N/C-A催化剂在经过AAT测试之后催化活性数据Eonset和Ehw分别仅降低了约23m V和10m V,在-0.4 V电位下的极限扩散电流密度jd也只降低了约0.4%,而商业Pt/C催化剂相应的ORR电催化活性数据Eonset和Ehw却分别降低了约68m V和20m V,在-0.4 V电位下的极限扩散电流密度jd降低了约4.6%,说明Co-N/C-A具有良好的稳定长期稳定性。重要的是,过渡金属钴的添加能够改善催化剂的催化剂的机理使其按照四电子途径进行还原,N/C催化剂的在催化氧还原反应的过程的电子转移数目为2.7,而CoN/C-A催化剂的为4.1。要使所制备催化剂的活性达到最佳,金属添加量、热处理时间和温度都要控制在一定的值,最有条件为钴添加量为20%时800℃下热处理2h。
[Abstract]:The consumption of fossil energy and the pollution caused by it make the exploration of new energy become an important challenge for all countries in the world. Fuel cells have high energy conversion efficiency. Air electrode, which is an important part of fuel cell, is the key bottleneck to control and influence the performance of fuel cell. Especially, ORR in air battery is characterized by slow kinetics and diversity of reaction pathway. It is an important direction of development of fuel cells to find cheap and efficient cathodic electrocatalysts to replace precious metal platinum-based catalysts. In this paper, Polyaniline with low cost and high nitrogen content is used. Melamine is used to modify carbon nanotubes to prepare TM-N/C catalysts. At the same time, the preparation conditions such as heat treatment time are optimized. The electrochemical activity was tested by linear voltammetry, the catalytic mechanism and stability were tested by rotating disk electrode, and the methanol resistance was measured according to the time-current curve. The morphology and structure of the catalyst were characterized by SEMS-XRDX XPS. The experimental results showed that the modification of carbon nanotubes by diazo source had obvious advantages over that modified by single nitrogen source. The initial oxygen reduction potential and peak potential of N / C catalyst can reach -35 MV and -113 MV respectively, and the addition of cobalt in transition metal can improve the activity of the catalyst. The initial potential and peak potential shifted positively at 5 MV and 25 MV, respectively, and the Co-N / C-A catalyst exhibited excellent methanol resistance. After AAT test, the catalytic activity data of Eonset and Ehw decreased only about 23mV and 10mV, respectively. At the potential of -0.4 V, the catalytic activity data of Co-N / C-A catalyst decreased only about 23mV and 10mV, respectively. The limit diffusion current density (JD) also decreased by about 0.4g, while the corresponding ORR electrocatalytic activity data (Eonset and Ehw) of commercial Pt/C catalysts decreased by 68mV and 20mV, respectively, and the limiting diffusion current densities (JD) at -0.4 V potential decreased by about 4.6g / d, respectively. It shows that Co-N/C-A has good stability and long-term stability. The addition of cobalt in transition metal can improve the mechanism of catalyst so that the number of electron transfer in the process of catalytic oxygen reduction of N / C catalyst is 2.7, and that of CoN/C-A catalyst is 4.1. The activity of the catalyst was optimized. The amount of metal added, the time of heat treatment and the temperature should be controlled at a certain value. The most suitable condition is that the amount of cobalt added is 20 鈩，

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