碳基过渡金属碳化物介孔材料及其电催化性能的研究

发布时间：2018-03-17 10:14

本文选题：过渡金属碳材料　切入点：离子液体　出处：《华东师范大学》2017年博士论文　论文类型：学位论文

【摘要】：为了保持人类社会的可持续发展,人们迫切需要开发利用清洁的能源。燃料电池(Fuel Cell)是一种将存在于氧化剂与燃料中的化学能直接转化为电能的技术,具有高能量密度和清洁的产能过程。然而燃料电池的大规模商业化中所遇到的瓶颈问题是电池阴极上非贵金属氧还原催化剂的性能不能满足实用的需要。因此,开发成本低,储量丰富的非贵金属高性能催化剂代替贵金属材料是推动燃料电池的大规模商业化的有效途径。过渡金属碳化物材料具有资源丰富、价格低廉、高导电性、高硬度、高熔点、优越的热稳定性和酸碱稳定性,以及类铂的电子结构和催化能力,因而在电极材料领域具有很大的应用潜力和研究价值。但现有的研究中对于过渡金属碳化物材料的制备合成及其电催化性能的研究相对较少。我们利用多种金属盐功能化的离子液体、钛-氮氧化钛基电极极板以及硬模版SBA-15分子筛等为基本材料,采用简单的涂覆热解法和灌注-热解-刻蚀法,制备了一系列新型负载过渡金属碳化物的钛-氮氧化钛基复合板基电极材料和碳基过渡金属碳化物有序介孔材料。并对所制备的材料进行了系统的分析与表征,研究了这些材料的电化学催化的性能,结果表明这些材料的电催化活性明显高于已报道同类材料中的最佳催化活性。具体研究内容如下:1.采用离子交换法设计制备了两种新型的过渡金属功能化的离子液体[Hmim]_2[Cr_2O_7](1-庚基-3-甲基咪唑铬酸盐)、[Bmim]_3[VO_4](1-丁基-3-甲基咪唑钒酸盐),按照文献合成了两种过渡金属功能化的离子液体[Bmim]_2[MoO_4](1-丁基-3-甲基咪唑钼酸盐)、[Bmim]_2[WO_4](1-丁基-3-甲基咪唑钼酸盐),并将这四种离子液体使用红外光谱(IR)、核磁共振谱(NMR)以及热重-差热分析(TG/DTA)的分析技术进行了系统的表征。确定了所制备离子液体的分子结构及其热解性质。2.利用高纯钛在氧气中加热再以三聚氰胺为氮源在惰性气体中加热的方法制备了钛-氮氧化钛极板。再利用离子液体涂覆-热解法成功将碳化钼、碳化钨、碳化铬和碳化钒粒子负载于钛-氮氧化钛极板表面,制得了Ti-TiN_xO_2-x-MoC、Ti-TiN_xO_2-x-WC、Ti-TiN_xO_2-x-Cr_7C_3、Ti-TiN_xO_2-x-V_8C_7等一系列复合电极材料。利用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、能谱(EDS)、X射线光电子能谱分析(XPS)等手段对上述电极进行了系统的表征,并进一步研究了上述复合电极材料在析氢反应、氧还原反应和乙醇的选择性部分氧化反应中的催化活性,与文献中报道的同类过渡金属碳化物相比,析氢起始电位提高了 20%-50%,氧还原起始电位提高了 10%-20%;与文献中报道的铂电极相比,对氧化产物乙醛的选择性提高18%-23%,证明以离子液体为前驱体制备的钛-氮氧化钛基过渡金属碳化物复合电极是一种多功能电极催化材料。3.将钼酸盐离子液体和SBA-15分子筛在常温和空气条件下研磨浸渍,浸渍后的样品在氮气中加热后刻蚀掉分子筛,即可得到大量的形貌一致的含有碳化钼纳米晶的碳基介孔材料。利用XRD、SEM、TEM、XPS等方法对上述碳化钼介孔材料进行了系统的表征,结果显示纳米晶尺寸均一,粒径约为3-5nm,材料比表面积为132m2 g-1,在析氢和氧还原反应中表现出了良好的双功能电催化剂性能,析氢反应的起始电位优于文献中的碳化钼纳米材料20-112 mV,氧还原反应的起始电位高于文献报道中的碳化钼材料90-220 mV,并在酸和碱两种环境下均可保持性能稳定。4.发展了基于钨酸盐离子液体合成碳化钨纳米碳基有序介孔材料的方法。通过研磨-热解-刻蚀的方法即可一次制备大量的碳化钨碳基介孔材料,介孔结构由碳包裹的碳化钨纳米晶组成,纳米晶尺寸均约为5 nm,比表面积144 m2 g-1,这种碳化钨材料可作为类铂的非贵金属双功能电催化剂,应用于析氢和氧还原反应,结果表明析氢反应的起始电位优于文献中的各种形貌的碳化钨纳米材料20-230mV,氧还原反应的起始电位高于文献报道同类材料10-300 mV,并且该种纳米碳化钨碳基介孔材料在酸、碱环境下显示了稳定的电化学性能。5.报道了碳化铬纳米介孔材料的合成方法。基于铬酸盐离子液体的特性,采用研磨-热解-刻蚀的方法,获取了由碳化铬纳米晶构成的碳基介孔碳化铬材料,碳化铬纳米晶尺寸约为2-4 nm,比表面积149 m~2 g~(-1)。该介孔碳化铬材料在析氢和氧还原反应中表现出色的催化活性,析氢反应的起始电位优于文献中的碳化铬材料70-200 mV,接近Pt的析氢催化活性。氧还原反应的起始电位高于文献中碳化铬材料80 mV,在酸、碱环境下电化学性能稳定。6.以钒酸盐离子液体为前驱体采用灌注刻蚀技术制备合成了碳化钒纳米晶构成的碳基介孔材料,碳化钒纳米晶尺寸约为5 nm,材料比表面积为133 m~2 g~(-1),作为非贵金属双功能电催化材料,将其应用于析氢和氧还原反应中,析氢反应的起始电位优于文献中碳化钒材料360 mV,氧还原反应的起始电位高于文献中碳化钒130 mV,酸和碱环境中均可保持性能稳定。综上所述,基于功能化离子液体合成过渡金属碳材料的方法开创了一条合成纳米过渡金属碳化物材料的新途径。此方法适用于多种过渡金属碳化物的合成,简单易行,能耗低,并且获得的多种过渡金属碳化物极板材料和过渡金属碳化物纳米粒子组成的碳基介孔材料的电催化性能十分优良,在燃料电池领域潜在着广阔的实用前景。
[Abstract]:In order to maintain the sustainable development of human society, there is an urgent need for the development and utilization of clean energy. Fuel cell (Fuel Cell) is a will exists in the oxidizer and fuel can be directly converted into electricity technology, the production process has high energy density and clean. However the bottleneck problem of large-scale commercial fuel cell encountered in the battery cathode on performance of non noble metal catalyst for oxygen reduction cannot meet the practical needs. Therefore, the development of low cost, high performance non noble metal catalyst rich instead of precious metal materials is an effective way to promote the large-scale commercial fuel cell. The transition metal carbide materials with abundant resources, price low, high conductivity, high hardness, high melting point, excellent thermal stability and pH stability, and platinum electronic structure and catalytic ability in electrode material field The application and research of great potential value. But the existing studies for the preparation of synthesis and catalytic properties of transition metal carbide electric material is relatively small. We use a variety of functional ionic liquid metal salt, titanium and nitrogen titanium oxide electrode and die version of SBA-15 molecular sieve as the basic material, using a simple coating pyrolysis and pyrolysis - reperfusion etching method, a series of novel supported transition metal carbide titanium titanium oxynitride composite plate and carbon based electrode materials of transition metal ordered mesoporous materials were prepared. And the prepared materials were analyzed and characterized the properties of the system, the electrochemical catalysis of these materials the results show that the electrocatalytic activity of these materials has the best catalytic activity was significantly higher than that reported in similar materials. The specific contents are as follows: 1. using the ion exchange method design Ionic liquid [Hmim]_2[Cr_2O_7] two transition metal model of the production function (1- -3- heptyl methyl imidazole chromate, [Bmim]_3[VO_4] (1-) butyl -3- methylimidazolium vanadate), according to the synthesis of the ionic liquid [Bmim]_2[MoO_4] two transition metal functionalized (1- butyl -3- methylimidazolium molybdate [Bmim]_2[WO_4] (1-), butyl -3- 2-methylimidazole), molybdate and the four kinds of ionic liquids using infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR) and thermogravimetric analysis (TG/DTA) analysis of the technology of the system characterized the molecular structure and properties of.2. prepared by pyrolysis of ionic liquid by heating in high purity titanium oxygen prepared titanium plate and titanium oxynitride using melamine as nitrogen source for heating in an inert gas in the system. Then using ionic liquid coating pyrolysis method successfully molybdenum carbide, tungsten carbide, chromium carbide and vanadium carbide particles Supported on titanium and nitrogen titanium oxide electrode surface, prepared with Ti-TiN_xO_2-x-MoC, Ti-TiN_xO_2-x-WC, Ti-TiN_xO_2-x-Cr_7C_3, Ti-TiN_xO_2-x-V_8C_7 and a series of composite electrode materials. By using X ray powder diffraction (XRD), scanning electron microscopy (SEM), energy spectrum (EDS), X ray photoelectron spectroscopy (XPS) characterization of the electrode system by means of further research and the composite electrode materials for hydrogen evolution catalytic activity in selective oxidation and oxygen reduction reaction in ethanol, compared with other transition metal carbides are reported, the initial analysis improves the 20%-50% potential of the hydrogen, oxygen reduction starting potential increase 10%-20%; compared with the platinum electrode literature in the report, the selective oxidation products of acetaldehyde increased 18%-23%, proved using ionic liquid as a precursor for the preparation of titanium and nitrogen titanium oxide based transition metal carbide composite electrode Is a kind of multifunctional electrode catalytic materials.3. molybdate ionic liquid and SBA-15 molecular sieve at room temperature and air abrasive impregnation, after impregnation of samples heated in nitrogen after etching can be obtained by molecular sieve carbon based mesoporous materials containing molybdenum carbide nanocrystals are consistent with the large number of morphology. The use of XRD, SEM. TEM, XPS and other methods were characterized on the molybdenum carbide mesoporous materials, results show that the nanocrystals with uniform size, the size is about 3-5nm, the surface area of the material is 132m2 g-1, the hydrogen and oxygen reduction reaction showed a good performance of electric double function catalyst, molybdenum carbide nano materials 20-112 mV the initial potential is better than that of the hydrogen evolution reaction in the literature, the onset potential for oxygen reduction is higher than that of molybdenum carbide material 90-220 mV reported in the literature, and in the two kinds of acid and alkali environment can maintain stable performance of.4. development based on tungstate from Methods the liquid synthesis of tungsten carbide nano carbon based ordered mesoporous materials. Through grinding method - pyrolysis etching a preparation of a large number of tungsten carbide carbon mesoporous material, mesoporous structure composed of nano crystalline tungsten carbide coated carbon composition, the nanocrystal size was about 5 nm. The specific surface area of 144 m2 g-1, the tungsten carbide material can be used as a platinum non noble metal bifunctional electrocatalyst, applied to hydrogen and oxygen reduction reaction. The results show that tungsten carbide nano materials with various morphologies of 20-230mV hydrogen evolution reaction in the literature is better than the initial potential, the oxygen reduction reaction initiation potential is higher than that reported similar materials 10-300 mV and, the nano tungsten carbide carbon based mesoporous materials in acid, alkali environment shows the electrochemical properties of.5. stable synthesized method of chromium carbide nano mesoporous materials. The characteristics of chromate based on ionic liquids, the grinding heat - moment solution Inhibition method, the mesoporous carbon chromium carbide material composed of nanocrystalline chromium carbide, chromium carbide nano crystal size is about 2-4 nm, the specific surface area of 149 m~2 g~ (-1). The mesoporous chromium carbide material reduction in the outstanding performance of the catalytic activity in hydrogen and oxygen, chromium carbide materials 70-200 mV of the initial potential of hydrogen evolution reaction is superior to that of the literature, the heractivity close to Pt. The onset potential for oxygen reduction is higher than that of chromium carbide materials in the literature in 80 mV,.6. acid, stable electrochemical performance of alkali environment with vanadate ionic liquids as precursor to synthesis of carbon based mesoporous materials Carbide vanadium is composed of nanocrystals used in etching technology, vanadium carbide nano crystal size is about 5 nm, the surface area of the material is 133 m~2 g~ (-1), as a non noble metal bifunctional catalytic materials and its application in hydrogen and oxygen reduction reaction, hydrogen evolution reaction is better than the initial potential Xian vanadium carbide material 360 mV, the initial potential of oxygen reduction reaction is higher than that in the literature of vanadium carbide 130 mV can maintain stable performance, acid and alkali environment. To sum up, the method of functional ionic liquids synthesis of transition metal based carbon materials created a new approach to synthesis of nano transition metal carbide materials. The synthesis of this method applicable to a variety of transition metal carbides has the advantages of simple operation, low energy consumption, the electrocatalytic properties of carbon based materials and pore obtained various transition metal carbide electrode material and transition metal carbide nanoparticles is very excellent, in the field of fuel cell potential broad practical prospect.

【学位授予单位】：华东师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36;TM911.4

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