微纳结构三氧化钨的可控制备及性能研究
发布时间：2018-07-25 06:08
【摘要】：微纳结构过渡金属氧化物的应用已经成为开启许多先进功能材料和智能设备潜力的重要工具。由于其具有不同的价态和价电子构型而拥有特殊的光、电、磁、力学性质,在变色、发光、催化、传感等许多方面都有应用。其中,一维过渡金属氧化物纳米材料因直接、快速的电子传输性能以及特殊的几何构型,有望成为未来纳米级电子器件的基元之一。此外,基于一维纳米结构有序自组装的多级微纳结构拥有独特的立体空间构架,其中许多具有大的可接触表面积与较多的活性位点数目,这种特殊的构效关系昭示了其应用的广阔前景。本论文以三氧化钨一维材料以及基于三氧化钨一维结构自组装的多级微纳结构材料为研究目标,利用水热法通过筛选反应体系,调整反应体系中各种条件,制备出晶体结构、微观尺度以及形貌可调控的一维结构三氧化钨及其自组装多级结构体系。进而对所合成的产物进行性能探究,包括应用于环己醇催化脱氢体系和环己烯催化氧化体系的催化性能,以及应用于电化学超级电容器的相关电化学性能。本论文所研究的内容主要涉及如下几个方面:(1)以钨酸钠、硝酸为反应物,柠檬酸、硫酸钠为分散剂和结构导向剂,通过水热法制备出沿着[001]轴方向生长的h-WO3纳米棒。值得一提的是,这些纳米棒是由直径、长度一致的h-WO3纳米线自组装而成。实验研究了以这种纳米棒结构三氧化钨作为催化剂,在无相转移剂、无酸性配体的条件下,以双氧水(H202)作为氧化剂催化氧化环己醇合成环己酮。结果表明,在温和的反应条件下(80℃,常压),纳米棒结构三氧化钨能够有效地提高双氧水的氧化能力,使得环己酮的产率由3.1%提高到78.6%,大大高于使用商业三氧化钨时环己酮的产率(43.0%)。同时催化剂也显示出较高的催化稳定性,这为合成环己酮提供了一种以三氧化钨纳米棒为催化剂、过氧化氢为氧化剂的绿色路径。(2)提出一种在不使用模板的条件下仅使用两种常见反应物合成一维结构三氧化钨及多级结构三氧化钨水合物的简便水热方法。仅依靠调节前驱溶液的pH值就可以得到纳米线自组装的三氧化钨棒及由纳米棒自组装的微纳多级结构(球状、盘状)三氧化钨水合物。与此同时,通过对比试验探究了 pH值对于产物晶体结构和形貌的影响机理。进一步,以所制备的微纳结构三氧化钨作为催化剂,以双氧水(H202)为氧化剂氧化环己烯合成己二酸。结果表明,在温和的反应条件(90℃、常压)下这种催化剂能够有效地提高双氧水催化氧化环己烯制备己二酸的产率。(3)以钨酸钠为钨源,通过水热法制备出基于一维结构自组装的三氧化钨水合物(h-WO3·0.33H2O)多级结构材料。该材料的结构除具有h-W03的三元通道和六元通道特征外,还在六元通道中堆积了水分子。这使得质子在晶体内部得以快速嵌入、脱嵌。同时,组成多级结构的h-WO3·0.33H2O纳米棒也给电子的传输提供了大量直接、快速的传输路径。正是由于稳定的晶体通道结构、h-WO3·0.33H2O材料的质子、电子双重导体作用以及特殊的多级结构使得h-WO3·0.33H2O材料具有很好的超级电容性能,在电流密度为0.5 Ag-1时具有391 Fg-1的比容量。同时,在电流密度为10 A g-1时仍能在循环2000次后稳定保持298 F g-1的比容量。
[Abstract]:The application of micro nanostructured transition metal oxides has become an important tool to open many advanced functional materials and intelligent devices. Because of their different valence and valence electron configurations, they have special light, electrical, magnetic and mechanical properties, and are applied in many aspects, such as discoloration, luminescence, catalysis, transmission and so on. Chemical nanomaterials are expected to be one of the basic elements of the future nanoscale electronic devices because of their direct, rapid electronic transmission properties and special geometric configurations. In addition, the multi-stage micro nanostructures based on the ordered self-assembled one-dimensional nanostructures have unique three-dimensional spatial structures, many of which have large contact surface area and more activity. The number of loci, this special structure-activity relationship shows the broad prospect of its application. In this paper, we use one dimensional tungsten trioxide material and multistage micro nano structure material based on one dimensional structure of tungsten oxide as the research target. By using the hydrothermal method, the various conditions in the reaction system are adjusted by screening the reaction system, and the crystal structure is prepared. The one-dimensional structure of tungsten trioxide and its self-assembled multistage structure system have been investigated, including the catalytic performance of cyclohexanol catalytic dehydrogenation system and cyclohexene catalytic oxidation system, as well as the related electrochemical properties of electrochemical supercapacitors. The main contents of this study are as follows: (1) the h-WO3 nanorods which grow along the [001] axis are prepared by sodium tungstate and nitric acid as reactant, citric acid, sodium sulfate as dispersant and structural guide. It is worth mentioning that these nanorods are self assembled by the diameter, uniform length of h-WO3 nanowires. The synthesis of cyclohexanone by the catalytic oxidation of cyclohexanol with hydrogen peroxide (H202) as an oxidizing agent under the condition of no phase transfer agent and no acidic ligand is investigated. The results show that the nanorod structure of tungsten oxide can effectively improve oxygen oxygen in hydrogen peroxide under mild reaction conditions (80 degrees C, atmospheric pressure). The yield of cyclohexanone increased from 3.1% to 78.6%, greatly higher than the yield of cyclohexanone (43%) when using commercial tungsten trioxide (43%). The catalyst also showed high catalytic stability. This provides a green path for synthesis of cyclohexanone with a tungsten trioxide nanorod as the catalyst and hydrogen peroxide as a oxidant. (2) A simple and convenient hydrothermal method is used to synthesize tungsten trioxide and multistage tungsten trioxide hydrate with only two kinds of common reactants without the use of the template. The self-assembled tungsten trioxide rod and the nanorod self assembled micro nano structure (spherical, disk) can be obtained by adjusting the pH value of the precursor solution only by adjusting the value of the precursor solution. At the same time, the influence mechanism of pH value on the crystal structure and morphology of the product was investigated by comparison test. Further, the synthesized tungsten oxide tungsten oxide was used as the catalyst to oxidize cyclohexene to adipic acid with hydrogen peroxide (H202) as the oxidizing agent. The results showed that under mild reaction conditions (90 degrees, atmospheric pressure) The catalyst can effectively improve the yield of hexandiacid prepared by hydrogen peroxide catalyzed oxidation of cyclohexene. (3) a tungsten trioxide hydrate (h-WO3. 0.33H2O) multistage structure based on one dimensional self assembly was prepared by hydrothermal method using sodium tungstate as the tungsten source. The structure of this material has the characteristics of three yuan channel and six element channel of h-W03. Water molecules are stacked in the six element channel. This allows protons to be embedded quickly and inlaid in the crystal. At the same time, the multistage structure of the h-WO3. 0.33H2O nanorods also provides a large number of direct and rapid transmission paths for the transmission of electrons. It is due to stable crystal channel structure, proton and electronic dual conduction of h-WO3. 0.33H2O materials The body effect and the special multistage structure make the h-WO3 0.33H2O material have good supercapacitor performance and have a specific capacity of 391 Fg-1 when the current density is 0.5 Ag-1. At the same time, the specific capacity of 298 F g-1 can still be maintained at the current density of 10 A g-1.
【学位授予单位】：合肥工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ136.13
本文编号：2142859
[Abstract]:The application of micro nanostructured transition metal oxides has become an important tool to open many advanced functional materials and intelligent devices. Because of their different valence and valence electron configurations, they have special light, electrical, magnetic and mechanical properties, and are applied in many aspects, such as discoloration, luminescence, catalysis, transmission and so on. Chemical nanomaterials are expected to be one of the basic elements of the future nanoscale electronic devices because of their direct, rapid electronic transmission properties and special geometric configurations. In addition, the multi-stage micro nanostructures based on the ordered self-assembled one-dimensional nanostructures have unique three-dimensional spatial structures, many of which have large contact surface area and more activity. The number of loci, this special structure-activity relationship shows the broad prospect of its application. In this paper, we use one dimensional tungsten trioxide material and multistage micro nano structure material based on one dimensional structure of tungsten oxide as the research target. By using the hydrothermal method, the various conditions in the reaction system are adjusted by screening the reaction system, and the crystal structure is prepared. The one-dimensional structure of tungsten trioxide and its self-assembled multistage structure system have been investigated, including the catalytic performance of cyclohexanol catalytic dehydrogenation system and cyclohexene catalytic oxidation system, as well as the related electrochemical properties of electrochemical supercapacitors. The main contents of this study are as follows: (1) the h-WO3 nanorods which grow along the [001] axis are prepared by sodium tungstate and nitric acid as reactant, citric acid, sodium sulfate as dispersant and structural guide. It is worth mentioning that these nanorods are self assembled by the diameter, uniform length of h-WO3 nanowires. The synthesis of cyclohexanone by the catalytic oxidation of cyclohexanol with hydrogen peroxide (H202) as an oxidizing agent under the condition of no phase transfer agent and no acidic ligand is investigated. The results show that the nanorod structure of tungsten oxide can effectively improve oxygen oxygen in hydrogen peroxide under mild reaction conditions (80 degrees C, atmospheric pressure). The yield of cyclohexanone increased from 3.1% to 78.6%, greatly higher than the yield of cyclohexanone (43%) when using commercial tungsten trioxide (43%). The catalyst also showed high catalytic stability. This provides a green path for synthesis of cyclohexanone with a tungsten trioxide nanorod as the catalyst and hydrogen peroxide as a oxidant. (2) A simple and convenient hydrothermal method is used to synthesize tungsten trioxide and multistage tungsten trioxide hydrate with only two kinds of common reactants without the use of the template. The self-assembled tungsten trioxide rod and the nanorod self assembled micro nano structure (spherical, disk) can be obtained by adjusting the pH value of the precursor solution only by adjusting the value of the precursor solution. At the same time, the influence mechanism of pH value on the crystal structure and morphology of the product was investigated by comparison test. Further, the synthesized tungsten oxide tungsten oxide was used as the catalyst to oxidize cyclohexene to adipic acid with hydrogen peroxide (H202) as the oxidizing agent. The results showed that under mild reaction conditions (90 degrees, atmospheric pressure) The catalyst can effectively improve the yield of hexandiacid prepared by hydrogen peroxide catalyzed oxidation of cyclohexene. (3) a tungsten trioxide hydrate (h-WO3. 0.33H2O) multistage structure based on one dimensional self assembly was prepared by hydrothermal method using sodium tungstate as the tungsten source. The structure of this material has the characteristics of three yuan channel and six element channel of h-W03. Water molecules are stacked in the six element channel. This allows protons to be embedded quickly and inlaid in the crystal. At the same time, the multistage structure of the h-WO3. 0.33H2O nanorods also provides a large number of direct and rapid transmission paths for the transmission of electrons. It is due to stable crystal channel structure, proton and electronic dual conduction of h-WO3. 0.33H2O materials The body effect and the special multistage structure make the h-WO3 0.33H2O material have good supercapacitor performance and have a specific capacity of 391 Fg-1 when the current density is 0.5 Ag-1. At the same time, the specific capacity of 298 F g-1 can still be maintained at the current density of 10 A g-1.
【学位授予单位】：合肥工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ136.13
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