氮掺杂石墨烯在电催化氧还原反应中活性的研究

发布时间：2018-04-23 12:57

本文选题：石墨烯 + 掺杂　；参考：《东南大学》2015年硕士论文

【摘要】：质子交换膜燃料电池是一种具有高能源转换效率与低污染等优点的燃料电池。这类电池一般以氢气作为燃料,氧气作氧化剂,其工作效率很大程度取决于电池阴极上的氧还原反应(Oxygen Reduction Reaction, ORR)速率。但在通常情况下,该反应的速率较低,因此需要加入合适的催化剂来加速反应,进而提高电池的工作效率。近年来随着碳材料(例如石墨烯、碳纳米管等)研究的日益深入,已有大量数据表明与商业化的含铂催化剂相比,氮掺杂碳材料也具有显著的氧还原催化活性。同时因碳材料具有价格低廉、稳定性高等优点,而被视为在未来可能得到大规模应用的一类氧还原反应催化剂。本论文主要是围绕氮掺杂石墨烯作为氧还原反应催化剂所开展的一些工作。(1)从合成体系入手,在水热法制备氮掺杂石墨烯的基础上,以氧还原催化性能为判断依据,从不同溶剂、不同氮源两个方面探讨了在本论文的实验条件下氮掺杂石墨烯的最佳合成环境。在此基础上,进一步掺入金属元素,制备得到了具有良好氧还原催化活性的铁钴氮共掺杂石墨烯。并结合X射线光电子能谱、拉曼光谱、电化学等检测方法,推断氮、氧、碳与金属元素在该体系中对氮掺杂石墨烯的结构与催化性能所具有的影响。(2)从初始氧化石墨烯的氧化程度入手,通过使用不同氧化剂、延长反应时间、增大氧化剂与石墨的配比等途径,合成了具有不同含氧量的氧化石墨烯,并以此为碳源,双氰胺为氮源,制备得到了一系列氮掺杂石墨烯,通过电化学测试以评价初始氧化石墨烯的氧化程度对氮掺杂石墨烯氧还原催化性能的影响。结果表明,在本论文的实验条件下,以氧化程度较高的氧化石墨烯为碳源时,制得的氮掺杂石墨烯表现出以四电子途径为主导的反应过程,氧还原催化性能较高。(3)从最终的氮掺杂石墨烯入手,尝试用强还原剂水合肼与氢碘酸对氮掺杂石墨烯进行还原以去除其中残留的含氧基团,从而提高氮掺杂石墨烯的氧还原催化性能。电化学测试表明,经水合肼和氢碘酸作用后氮掺杂石墨烯的电流密度有所降低,而起峰电位皆有所负移。同时借助x射线光电子能谱、扫描电子显微镜等表征手段从组成与形貌上对该现象作出推断解释。结果表明,氢碘酸作用后会导致氮掺杂石墨烯原本的层状结构发生聚合；而水合肼虽然对氮掺杂石墨烯有一定还原作用,但会导致氮掺杂石墨烯中氮含量的下降,降低氧还原催化性能。
[Abstract]:Proton exchange membrane fuel cell (PEMFC) is a fuel cell with high energy conversion efficiency and low pollution. Hydrogen is generally used as fuel and oxygen as oxidant. The efficiency of this kind of cells depends largely on the rate of oxygen Reduction reaction (ORR) on the cathode of the cell. But in general, the reaction rate is low, so it is necessary to add the appropriate catalyst to accelerate the reaction and improve the efficiency of the battery. In recent years, with the increasing research of carbon materials (such as graphene, carbon nanotubes, etc.), a large number of data show that nitrogen doped carbon materials also have significant catalytic activity for oxygen reduction compared with commercial platinum catalysts. At the same time, because of the advantages of low cost and high stability, carbon materials are regarded as a kind of oxygen reduction catalysts which may be widely used in the future. This thesis mainly focuses on the work of nitrogen-doped graphene as a catalyst for oxygen reduction reaction, starting from the synthesis system, on the basis of hydrothermal preparation of nitrogen-doped graphene, and judging the catalytic performance of oxygen reduction. The optimum synthesis environment of nitrogen-doped graphene was studied from two aspects of different solvents and different nitrogen sources under the experimental conditions in this paper. On this basis, the Fe-Co N co-doped graphene with good catalytic activity for oxygen reduction was prepared by adding metal elements. Combined with X-ray photoelectron spectroscopy, Raman spectroscopy and electrochemical methods, nitrogen, oxygen, The effect of carbon and metal elements on the structure and catalytic performance of nitrogen-doped graphene in this system. Graphene oxide with different oxygen content was synthesized by increasing the ratio of oxidant to graphite, and a series of nitrogen-doped graphene was prepared by using it as carbon source and dicyandiamide as nitrogen source. The effect of the oxidation degree of the initial graphene oxide on the catalytic performance of nitrogen-doped graphene oxide reduction was evaluated by electrochemical test. The results show that the nitrogen-doped graphene exhibits a four-electron pathway when graphene oxide with high degree of oxidation is used as carbon source under the experimental conditions in this paper. Starting with the final nitrogen-doped graphene, the nitrogen-doped graphene was reduced by strong reductant hydrazine hydrate and hydroiodate to remove the residual oxygen groups. Therefore, the catalytic performance of nitrogen-doped graphene in oxygen reduction was improved. The electrochemical measurements showed that the current density of nitrogen-doped graphene was decreased and the peak potential shifted negatively after the action of hydrazine hydrate and iodate acid. At the same time, by means of X-ray photoelectron spectroscopy and scanning electron microscope, this phenomenon is inferred and explained in terms of composition and morphology. The results show that hydrogen iodate can lead to the polymerization of the original layered structure of nitrogen-doped graphene, while hydrazine hydrate can reduce the nitrogen content of nitrogen-doped graphene, although it can reduce the content of nitrogen-doped graphene. Reduce the catalytic performance of oxygen reduction.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ127.11;TM911.4

【相似文献】