碳负载碳化钨材料的制备及其电催化性能

发布时间：2018-05-29 22:09

本文选题：碳化钨 + 介孔材料　；参考：《浙江工业大学》2014年硕士论文

【摘要】：近年来,作为替代贵金属铂可应用于直接甲醇燃料电池的碳化钨材料越来越引起人们的关注。由于碳化钨具有与贵金属铂相似的表面电子结构,因此在一些化学和电化学反应中展现出奇特的类铂催化活性。然而与金属铂相比,碳化钨材料的催化性能仍然较低。因此,如何制备催化活性高的碳化钨材料成为当前国内外研究的热点。本文在综述碳化钨材料的制备方法及电催化性能的基础上,分别采取两种方法来制备碳负载碳化钨复合材料,并研究了其催化活性。一方面,通过液相移植的方法,以乙醇为分散剂,磷钨酸(PTA)为钨源,介孔分子筛SBA-15和扩孔后的CMK-3型介孔碳(OMC)为模板和载体,通过调整浸渍时间,一步还原碳化得到具有大比表面积、高催化活性的碳负载碳化钨材料。实验结果表明,以正硅酸乙酯(TEOS)为SiO2前驱体,P123为结构导向剂制得的介孔分子筛SBA-15具有规整有序的孔道及大的比表面积,孔径可达到7nm,更利于钨源PTA的进入。而经过扩孔后的有序介孔碳材料CMK-3的孔径也可达到7-8nm,使得碳化钨的负载量可以尽可能的多。通过X-射线衍射(XRD)、低温氮气吸脱附(BET)、能量X-射线光谱(EDX)和场发射透射电子显微镜(TEM)等表征方法可知,复合材料具有规整的介孔结构,较大的比表面积,因而两种材料均在酸性甲醇溶液中表现出了良好的催化甲醇电氧化的催化性能。另一方面,通过离子交换法,利用阴离子交换树脂吸附钨酸根,通过分析树脂材料的热重曲线以及红外吸收曲线,得出最佳的碳化程序,经过一步还原碳化得到具有大的比表面积的碳负载碳化钨WC/C复合材料。采用XRD、EDX、 TEM、 BET等表征手段对复合材料的物相结构、化学组成、表面形貌等进行研究。结果表明WC/C材料中碳化钨大部分以WC的形式存在,WC在碳基体上分散均匀。在中性对硝基苯酚溶液中的测试结果表明该材料对对硝基苯酚的还原有很好的催化作用,在酸性甲醇溶液中的电化学测试结果表明该材料对甲醇氧化亦具有催化性能。
[Abstract]:In recent years, tungsten carbide, which can be used as a substitute for precious metal platinum for direct methanol fuel cells, has attracted more and more attention. Because tungsten carbide has a surface electronic structure similar to that of precious metal platinum, it exhibits unique platinum-like catalytic activity in some chemical and electrochemical reactions. However, the catalytic performance of tungsten carbide is still lower than that of platinum. Therefore, how to prepare tungsten carbide materials with high catalytic activity has become a hot topic at home and abroad. Based on the review of the preparation methods and electrocatalytic properties of tungsten carbide materials, two methods were adopted to prepare carbon-supported tungsten carbide composites, and their catalytic activity was studied. On the one hand, with ethanol as dispersant, phosphotungstate as tungsten source, mesoporous molecular sieve SBA-15 and expanded CMK-3 mesoporous carbon montmorillonite as template and carrier, the impregnation time was adjusted. Carbon supported tungsten carbide materials with large specific surface area and high catalytic activity were obtained by one step reduction carbonization. The experimental results show that the mesoporous molecular sieve SBA-15 prepared by using tetraethyl orthosilicate (TEOS) as the precursor of SiO2 P123 has regular and ordered pore channels and large specific surface area, and the pore size can reach 7 nm, which is more favorable for the entry of tungsten source PTA. The pore size of ordered mesoporous carbon material CMK-3 after reaming can reach 7-8 nm, which makes the loading amount of tungsten carbide as much as possible. By means of X ray diffraction (XRD), low temperature nitrogen adsorption and desorption (BET), energy X- ray spectroscopy (EDX) and field emission transmission electron microscopy (TEM), it is found that the composite has regular mesoporous structure and large specific surface area. Therefore, both materials exhibit good catalytic performance for methanol electrooxidation in acidic methanol solution. On the other hand, the best carbonation procedure was obtained by analyzing the thermogravimetric curves and infrared absorption curves of resin materials by ion exchange method and adsorption of tungstate with anion exchange resin. Carbon supported tungsten carbide (WC/C) composites with large specific surface area were prepared by one step reduction carbonization. The phase structure, chemical composition and surface morphology of the composites were studied by means of XRDX EDX, TM, BET and so on. The results show that most of the tungsten carbide in WC/C material exists in the form of WC, and the WC is dispersed uniformly on the carbon matrix. The results in neutral p-nitrophenol solution showed that the material could catalyze the reduction of p-nitrophenol, and the electrochemical test in acid methanol solution showed that the material also had catalytic activity for methanol oxidation.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TQ136.13;TM911.4

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