杂原子掺杂石墨烯气凝胶的高效氧气还原催化剂的构筑

发布时间：2018-05-07 08:31

  本文选题：杂原子掺杂 + 石墨烯气凝胶　； 参考：《长春理工大学》2016年硕士论文

【摘要】：具有低的实际操作温度、对环境零污染、高的能量密度和较长的寿命等特点,使得直接甲醇燃料电池(DMFCs)得到广泛关注。然而,DMFCs阴极动力学反应速率很慢,从而影响了DMFCs的实际应用。迄今为止,铂系催化剂具有一些优良的性质(如较低的过电位、高的电流密度等),因而应用范围广泛。但是,铂系催化剂也存在许多缺点,例如价格昂贵、有一定的毒性、不稳定等,这些缺陷在不同程度上都影响了直接甲醇燃料电池的更广泛的应用。近些年来,在氧还原反应(ORR)中,杂原子掺杂的碳材料是一类具有高催化活性的催化剂。本文采用溶剂热和高温热处理的方法分别制备了三种石墨烯气凝胶:首先,5-氨基-1,3,4-噻重氮-2-硫醇(C2H3N3S2)作为硫源与氮源,与氧化石墨(GO)进行水热反应,形成的聚5-氨基-1,3,4-噻重氮-2-硫醇修饰的石墨烯水凝胶,再经过冷冻干燥得到聚5-氨基-1,3,4-噻重氮-2-硫醇修饰的石墨烯气凝胶,经过高温煅烧得到氮硫共掺杂的石墨烯气凝胶(N-S-GAs);其次,用2,6-二氨基吡啶作为氮源通过与GO进行水热反应,然后对形成的水凝胶进行冷冻干燥和高温煅烧得到氮掺杂的气凝胶,制备了单独氮掺杂石墨烯气凝胶(N-GAs);最后,为了改善N-GAs的性能,通过原位的方法在第二个体系中引入铁离子,对一定比例的2,6-二氨基吡啶、硝酸铁(Fe(NO3)3)和GO的混合溶液进行水热反应,然后经过冷冻干燥和高温煅烧后得到铁氮双掺的石墨烯气凝胶(Fe-N-GAs)。经过高温煅烧后,铁离子转变成碳化铁纳米粒子,并研究金属加入量对催化性能的影响,并研究了其在酸性条件下的催化性能。分别对所形成的三种催化剂进行了结构表征和电化学测试的表征,例如采用扫描电子显微技术(SEM)和透射电子显微技术(TEM)对所制备的复合物的形貌进行表征。使用氮吸附脱附等温线、拉曼光谱分析和X射线光电子能谱技术对材料的孔结构和结构进行分析。采用旋转圆盘电极实验(RDE)和旋转环盘电极实验(RRDE)对所制备的催化剂在碱性介质中对氧气还原的催化活性。测试结果表明所制备的催化剂有很好的催化性能,如较正的起峰电位、较大的极限电流密度以及好的耐甲醇性能和稳定性等。因此,在碱性介质中杂原子掺杂的石墨烯气凝胶是一类有前景的阴极氧气还原催化剂。
[Abstract]:With the characteristics of low operating temperature, zero pollution to environment, high energy density and long life, DMFCsof direct methanol fuel cell (DMFCs) have been paid more and more attention. However, the cathodic kinetic reaction rate of DMFCs is very slow, which affects the practical application of DMFCs. So far, the platinum catalyst has some excellent properties (such as low overpotential, high current density and so on), so it is widely used. However, platinum catalysts also have many disadvantages, such as high price, toxicity, instability and so on. These defects affect the wider application of direct methanol fuel cells in varying degrees. In recent years, hetero-atom doped carbon is a kind of catalyst with high catalytic activity in oxygen reduction reaction (ORR). In this paper, three kinds of graphene aerogels were prepared by solvothermal and high temperature heat treatment. Firstly, 5-amino-1-aniline 4-thiazo-4-thiazo-2-mercaptan (C2H3N3S2) was used as sulfur and nitrogen source, and hydrothermal reaction with graphite oxide (GOO) was carried out. The graphene hydrogel modified by poly5-amino-1-thiazo-4-thiazo-2-mercaptan was prepared by freeze-drying, and then the graphene aerogel modified by poly5-amino-1-diazo-3-thiazo-4-thio-2-mercaptan was obtained by freeze-drying. After high temperature calcinations, N-S-GAs-doped graphene aerogels were prepared. Secondly, N-doped aerogels were prepared by freeze-drying and calcining of N-doped aerogels by hydrothermal reaction with go with 2O6-diaminopyridine as nitrogen source, then the resulting hydrogels were freeze-dried and calcined at high temperature to obtain nitrogen-doped aerogels. In order to improve the properties of N-GAs, iron ions were introduced into the second system by in situ method. The mixed solution of ferric nitrate Fegno _ 3) and go was hydrothermal reacted, and then freeze-dried and calcined at high temperature to obtain Fe-N-GAsN aerogel mixed with iron and nitrogen. After high temperature calcination, iron ions were transformed into iron carbide nanoparticles, and the effect of metal addition on the catalytic performance was studied. The catalytic properties of iron ions in acidic conditions were also studied. The structure and electrochemical properties of the three catalysts were characterized, such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to characterize the morphology of the composites. Nitrogen adsorption and desorption isotherms, Raman spectroscopy and X-ray photoelectron spectroscopy were used to analyze the pore structure and structure of the materials. The catalytic activity of the prepared catalyst for oxygen reduction in alkaline medium was studied by rotating disk electrode (RDE) and rotating ring disk electrode (RRDE). The results show that the prepared catalysts have good catalytic performance, such as positive peak starting potential, high limit current density, good methanol resistance and stability. Therefore, graphene aerogels doped with heteroatoms in alkaline media are a promising cathodic oxygen reduction catalyst.
【学位授予单位】：长春理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36
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本文编号：1856198