金属掺杂氧还原碳催化剂的制备及性能研究

发布时间：2018-04-13 18:20

本文选题：金属掺杂碳催化剂 + 多元共掺杂　；参考：《中国矿业大学》2017年硕士论文

【摘要】：燃料电池作为一种清洁高效的新能源技术,具有非常广阔的应用前景。由于阴极催化效率明显低于阳极,所以燃料电池的电催化研究仍主要集中于阴极催化剂的开发上。目前,阴极催化活性较高的催化剂多为贵金属铂基催化剂,但由于其成本高、储量少、耐甲醇能力低且稳定性差等缺陷,严重限制了燃料电池的商业化发展。近年来大量研究表明Fe、Co等非贵过渡金属掺入碳的网络结构能明显改善碳催化剂的氧还原(ORR)活性,有望替换贵金属催化剂。为开发高活性、低成本且稳定性优良,耐甲醇渗透性好的金属掺杂碳催化剂,本文尝试将锗原子掺入碳的网络结构,开发新型非贵金属锗、锗氮共掺杂碳催化剂,及通过非贵金属铁与非金属多元掺杂等方式,利用廉价生物质开发低廉高效碳催化剂。具体研究内容如下:1.通过气相沉积法,以四乙基锗为锗源制备新型锗掺杂碳纳米管(Ge-CNTs)。通过扫描电镜(SEM)、透射电镜(TEM)、比表面积测定仪(BET)和X-射线光电子能谱(XPS)等手段对其形貌、比表面积及元素组成等进行表征分析,结果表明锗原子可以掺入碳纳米管结构网络。同时电化学测试表明碱性条件下,Ge-CNTs的ORR活性明显高于无掺杂CNTs,且耐甲醇性能和稳定性能均优于47.6 wt%商业Pt/C催化剂。Koutechy-Levich方程计算显示Ge-CNTs表观电子转移数明显高于CNTs,表明氧分子在Ge-CNTs表面上吸附方式不同于无掺杂CNTs,这可能由于锗原子掺入碳的网络结构,引起碳纳米管表面的电荷分布及能带等电子特性发生改变。2.通过气相沉积法,以四乙基锗为锗源,苯胺为氮源制备锗氮共掺杂碳纳米管(GeN-CNTs)。通过SEM、TEM、BET、XPS等手段对其形貌、比表面积及元素组成等进行表征分析,结果表明锗原子和氮原子可以同时掺入到碳纳米管结构网络。电化学测试表明碱性条件下GeN-CNTs的ORR活性明显高于N-CNTs,且耐甲醇性能,稳定性能均优于47.6 wt%商业Pt/C。Koutechy-Levich方程计算显示GeN-CNTs表观电子转移数大于3,表明其表面氧还原反应多为四电子高效反应途径,显示锗和氮原子的掺入碳的网络结构能够改变氧分子吸附方式。3.通过快速高温热解生物质桂花果中活性物质、Fe_2(SO_4)_3及二氰二胺混合物,制备N、S、P和Fe多元掺杂碳纳米孔与碳纳米管复合材料。通过EDS、XPS、BET等手段,对其结构、形貌、元素组成等进行表征分析,结果表明N、S、P和Fe等元素可掺入碳纳米结构网络中(Fe掺入量较小)。同时电化学测试表明所制备的复合材料在碱性和酸性条件下均显示优异ORR活性、耐甲醇性能和稳定性能。Koutechy-Levich方程计算显示所制备的复合材料表面上氧分子发生还原反应时的电子转移数在碱性和酸性条件下都接近4电子过程,表明N、S、P和Fe多元掺杂有利于氧分子的侧基吸附。
[Abstract]:As a clean and efficient new energy technology, fuel cell has a very broad application prospect.Because the efficiency of cathode catalysis is obviously lower than that of anode, the electrocatalysis of fuel cell is mainly focused on the development of cathode catalyst.At present, most of the catalysts with high cathodic activity are precious metal platinum based catalysts. However, the commercial development of fuel cells is seriously restricted because of its high cost, low reserves, low methanol tolerance and poor stability.In recent years, a large number of studies have shown that the network structure of non-expensive transition metals, such as FeCo, can obviously improve the oxygen reduction ORR activity of carbon catalysts, which is expected to replace noble metal catalysts.In order to develop metal-doped carbon catalysts with high activity, low cost, good stability and good methanol permeability, this paper attempts to develop a new type of non-noble metal germanium and germanium nitrogen co-doped carbon catalysts by adding germanium atoms into the structure of carbon network.The low-cost and high-efficient carbon catalyst was developed by non-precious metal iron and non-metallic multi-doping.The specific contents of the study are as follows: 1.A new germanium doped carbon nanotube (Ge-CNTsN) was prepared by vapor deposition with tetraethyl germanium as a germanium source.The morphology, specific surface area and elemental composition were characterized by SEM, TEM, BET and X- ray photoelectron spectroscopy (XPS). The results showed that germanium atoms could be doped into CNT structure network.At the same time, electrochemical test showed that the ORR activity of Ge-CNTs in alkaline condition was significantly higher than that of undoped CNTs, and the methanol resistance and stability of Ge-CNTs were better than 47.6 wt% commercial Pt/C catalysts. Koutechy-Levich equation calculation showed that the apparent electron transfer number of Ge-CNTs was significantly higher than that of CNTs, and the apparent electron transfer number of Ge-CNTs was obviously higher than that of CNTs.The adsorption mode of Ge-CNTs is different from that of doped CNTs, which may be due to the network structure of carbon doped with germanium atoms.The surface charge distribution and energy band of carbon nanotubes are changed. 2. 2.GE N-doped carbon nanotubes were prepared by vapor deposition with tetraethylgermanium as germanium source and aniline as nitrogen source.The morphology, specific surface area and elemental composition were characterized by means of SEM-TEMP-BET-XPS. The results showed that germanium atom and nitrogen atom could be doped into CNT structure network at the same time.Electrochemical tests showed that the ORR activity of GeN-CNTs was significantly higher than that of N-CNTs under alkaline conditions, and the methanol resistance of GeN-CNTs was higher than that of N-CNTs.The stability of GeN-CNTs was better than that of 47.6 wt% commercial Pt/C.Koutechy-Levich equation. The results showed that the apparent electron transfer number of GeN-CNTs was greater than 3, which indicated that the surface oxygen reduction reaction was mainly a four-electron high efficiency reaction pathway.It is shown that the network structure of doped carbon with germanium and nitrogen atoms can change the adsorption mode of oxygen molecule. 3.The composite of carbon nanotubes and carbon nanotubes (CNTs) was prepared by pyrolysis of the active substances Fe2SO4Sn3 and dicyandiamide in biomass Osmanthus osmanthus fruit at high temperature.The structure, morphology and elemental composition were characterized by means of EDSS-XPS-BET. The results showed that the elements such as NbSfP and Fe could be doped into the carbon nanostructure network with relatively small amount of Fe doped.At the same time, the electrochemical test showed that the composites exhibited excellent ORR activity in alkaline and acidic conditions.The calculation of methanol resistance and stability. Koutechy-Levich equation showed that the electron transfer number of oxygen molecules on the surface of the composites was close to 4 in alkaline and acidic conditions.The results show that the doping of NbS- P and Fe is beneficial to the side group adsorption of oxygen molecules.
【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;TM911.4

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