非金属掺杂功能碳材料电催化性能的研究

发布时间：2018-03-23 16:54

本文选题：砷掺杂碳纳米管　切入点：砷氮共掺杂碳纳米管　出处：《中国矿业大学》2017年硕士论文

【摘要】：氧还原反应(Oxygen Reduction Reaction,ORR)和氧析出反应(Oxygen Evolution Reaction,OER)作为能量储存和转换过程中的两个关键电化学反应,一直是电催化领域的研究热点。目前围绕ORR和OER反应所开发的催化剂多是以Pt、Ru和Ir等贵金属催化剂为主,并取得一定进展。然而,贵金属储量少和价格高等缺点,却使其一直难以规模化应用。近年来大量研究表明新近出现成本低廉的非金属掺杂碳材料展现出较好的ORR和OER电催化性能,可望取代贵金属催化剂。为开发出活性更加优异的非金属掺杂碳催化剂,本文尝试制备了新型砷掺杂、砷氮共掺杂的碳纳米管和氮掺杂有序介孔碳材料,用于ORR和OER的电催化并对其催化机制进行探讨。主要内容如下:(1)新型砷掺杂碳纳米管(As-CNTs)的制备及其电催化性能考察采用化学气相沉积法(CVD),将含有三苯基砷的二甲苯溶液在高温下气化热解,制备As-CNTs,并对获得的As-CNTs结构、组成等进行表征分析,结果表明原子半径较大的砷原子可以掺入到碳纳米管的网络结构。电化学测试表明所制备的As-CNTs在碱性条件下展现出较好的ORR和OER电催化活性,显示砷原子掺杂能明显改善碳纳米管的ORR和OER电催化活性。同时,密度泛函理论计算表明砷原子周边的碳原子的净电荷由变成了电负性,且能隙降低,进一步从理论上证实砷原子掺杂有利于提高碳纳米管的ORR和OER电催化性能。(2)新型砷氮共掺杂碳纳米管(AsN-CNTs)的制备及其电催化性能考察为了进一步提高砷掺杂碳材料的催化活性,本文又尝试合成了砷氮二元共掺杂碳纳米管(AsN-CNTs),并对所制备的材料进行结构表征和元素含量分析,证实砷元素和氮元素的成功掺杂。电化学测试结果表明:在碱性条件下,AsN-CNTs的ORR电催化活性明显优于氮掺杂碳纳米管(N-CNTs),表明As和N原子之间存在协同作用。同时,砷氮共掺碳纳米管还表现出了优异的OER催化活性。理论计算结果表明砷原子和氮原子周围的碳原子净电荷发生改变,以展现出更多的活性位点,且能隙降低,更有利于ORR和OER电催化性能的提高。(3)掺氮碳材料中活性氮物种对ORR和OER催化性能的影响尽管掺氮碳材料在ORR和OER的应用已经取得了巨大的进展,然而,关于何种氮对ORR的起主要作用一直都没有定论。为此,本文以廉价的烟叶为原料,制备氮掺杂有序介孔碳材料(N-OMC),用二氰二胺用来调节氮的种类和含量,并在碱性和酸性条件下,同时对其ORR和OER催化活性进行测试分析,结果显示:在N-OMC中,吡啶氮和吡咯氮对ORR和OER催化活性的提高起主要作用,这对未来双功能催化剂的开发具有指导性意义。
[Abstract]:Oxygen Reduction reaction (ORR) and oxygen precipitation reaction (Oxygen Evolution reaction or er) are two key electrochemical reactions in energy storage and conversion. It has been a research hotspot in the field of electrocatalysis. At present, the catalysts developed around ORR and OER reactions are mainly precious metal catalysts, such as PTR Ru and ir, and some progress has been made. However, there are some disadvantages such as small reserves and high price of precious metals. In recent years, a large number of studies have shown that the low cost nonmetallic doped carbon materials exhibit good electrocatalytic properties of ORR and OER. It is expected to replace noble metal catalysts. In order to develop non-metal doped carbon catalysts with better activity, new arsenic doped, arsenic nitrogen co-doped carbon nanotubes and nitrogen-doped ordered mesoporous carbon materials have been prepared. The main contents of this paper are as follows: (1) preparation of new arsenic doped carbon nanotubes (As-CNTs) and its electrocatalytic properties. Chemical Vapor deposition (CVD) method was used to study the catalytic mechanism of ORR and OER. Benzene solution is pyrolyzed by gasification at high temperature, As-CNTswere prepared, and the structure and composition of the obtained As-CNTs were characterized and analyzed. The results show that arsenic atoms with larger atomic radius can be incorporated into the network structure of CNTs. Electrochemical tests show that the prepared As-CNTs exhibits good ORR and OER electrocatalytic activity under alkaline conditions. The results show that the doping of arsenic atom can obviously improve the ORR and OER electrocatalytic activity of carbon nanotubes. Meanwhile, the density functional theory calculation shows that the net charge of the carbon atom around the arsenic atom changes from electronegativity to electronegativity, and the energy gap decreases. It is further proved that arsenic atom doping is beneficial to the improvement of ORR and OER electrocatalytic properties of carbon nanotubes.) the preparation and electrocatalytic properties of new arsenic-nitrogen co-doped carbon nanotubes (AsN-CNTss) were investigated in order to further improve the catalytic activity of arsenic-doped carbon materials. In this paper, AsN-CNTsO was synthesized, and the structure and elemental content of the prepared materials were analyzed. The electrochemical test results showed that the ORR electrocatalytic activity of AsN-CNTs was obviously superior to that of N-CNTsN doped carbon nanotubes under alkaline conditions, indicating that there was a synergistic effect between as and N atoms. The results of theoretical calculation show that the net charge of carbon atoms around arsenic atom and nitrogen atom changes to show more active sites and the energy gap decreases. The effect of active nitrogen species in nitrogen-doped carbon materials on the catalytic performance of ORR and OER although the application of nitrogen-doped carbon materials in ORR and OER has made great progress, however, There has been no conclusion as to which nitrogen plays a major role in ORR. Therefore, N-doped ordered mesoporous carbon material (N-OMC) was prepared by using cheap tobacco leaves as raw materials. Dicyandiamide was used to regulate the type and content of nitrogen in alkaline and acidic conditions. At the same time, the catalytic activities of ORR and OER were tested and analyzed. The results showed that pyridine nitrogen and pyrrole nitrogen played a major role in the improvement of the catalytic activity of ORR and OER in N-OMC, which was instructive to the development of bifunctional catalysts in the future.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;O646

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