金属钼基化合物电极材料的制备及其电化学性能研究

发布时间：2018-06-13 19:16

本文选题：超级电容器 + 金属钼基化合物　；参考：《兰州理工大学》2017年硕士论文

【摘要】：金属钼基化合物因独特的电子导电性、多个可用的氧化态以及由较弱的范德华力耦合特殊的几何结构等特点。基于以上优点,使得金属钼基化合物成为超级电容器的的理想电极材料。本文针对金属钼基化合物,利用不同制备方法,成功合成出花状MoO_2/MoS_2复合电极材料。在此基础上,利用第三主族元素电负性的不同,进而制备并研究MoSe_2电极材料。此外,在正四价钼化合物的研究基础上,进一步探索正六价钼化合物的电化学性能,成功制备出取向不同的MoO_3电极材料。利用XRD、SEM、TEM、BET和Mapping等测试技术对所制备的材料的微观结构和形貌进行了分析,同时用循环伏安(CV)、恒电流充放电(PT)和电化学阻抗(EIS)等技术测试其电化学性能,并针对其电化学性能与结构的关系展开研究。主要研究内容和结果如下:一、以钼酸铵、九水硫化钠、硼氢化钠为原料,通过控制九水硫化钠的质量,采用简单水热法制备MoO_2/MoS_2电极材料。通过对产物进行结构表征,当九水硫化钠质量为0.75 g时所得到的MoO_2/MoS_2样品具有特殊的花状微球结构,这种特殊纳米微球结构有利于电解液离子的扩散。由于具有较好的导电性,特殊的花状结构以及MoO_2和MoS_2之间储能机制的协同效应,所制备的MoO_2/MoS_2电极材料具有良好的电化学性能,在5 mV s-1扫描速率下,MoO_2/MoS_2的比容量可以达到433.3 F g-1;在经过5000次循环后,比容量保持率为84.41%,相比纯的MoO_2(循环2000圈保持33.33%)和MoS_2(循环2000圈保持58.33%)具有优异的循环稳定性。二、以钼酸铵、硒粉、硼氢化钠为原料,采用简单水热法和后续的热处理工艺,成功合成了MoSe_2样品,研究MoSe_2样品的电化学性能。此外,还探究了Mo元素与处于同主族的O、S、Se化合而成的MoO_2、MoS_2及MoSe_2三中电极材料之间的电化学性能差异,进一步研究同主族不同电负性的非金属元素对于钼基化合物电极材料电化学性能的影响。结果显示所制备的MoSe_2具有独特的鸡冠花状结构和较高的电导性。电化学结果显示其倍率性能较MoO_2和MoS_2电极材料优异,在5 A g-1电流密度下,倍率性能可达75.6%。此外,为了探究MoSe_2的器件特性,用所制备的MoSe_2作为负极,自制活性炭(SHAC)作为负极,组装了MoSe_2//SHAC非对称电容器。MoSe_2//SHAC电容器在0~1.9 V的工作窗口下,电流密度为1 A g-1时,比容量可达62.08 A g-1。同时,能量密度可达31.1 Wh kg-1,在1 A g-1电流密度下进行循环稳定性测试,循环6000圈容量依旧可以保持初始容量的94%,仅仅衰减了6%。三、以钼酸钠为原料,去离子水为溶剂,利用硝酸调控pH并采用简单化学沉淀法制备不同取向的MoO_3,电化学测试发现当硝酸浓度为5.2 mol L-1时,MoO_3在(040)晶面择优生长。同时,在该条件下的MoO_3电极材料具有优异的电化学性能,电流密度为1 A g-1时容量可达531.85 F g-1,循环3500圈后保持初始容量的96%。在此基础上,用MoO_3做为负极,用分级纳米多孔碳(HNC-IPNs)做为正极,构建MoO_3//HNC-IPNs非对称超级电容器。该电容器在0~2.0 V的电位窗口下表现出优异的应用特性,在1 A g-1电流密度下其容量最高达到54.72 F g-1。同时,其能量密度和功率密度均优于AC//AC对称超级电容器。
[Abstract]:Metal molybdenum based compounds are characterized by unique electronic conductivity, many available oxidation states and special geometric structures coupled with weak van Edward forces. Based on the above advantages, molybdenum based compounds become ideal electrode materials for supercapacitors. In this paper, different preparation methods have been made for molybdenum based compounds. The MoO_2/MoS_2 composite electrode material was synthesized. On this basis, the MoSe_2 electrode materials were prepared and studied by the difference of the electronegativity of the third main elements. On the basis of the study of the positive tetravalent molybdenum compound, the electrochemical energy of the positive six valence molybdenum compound was further explored, and the different MoO_3 electrode materials with different orientation were successfully prepared. The microstructure and morphology of the prepared materials were analyzed by XRD, SEM, TEM, BET and Mapping. The electrochemical properties of the materials were measured by cyclic voltammetry (CV), constant current charge discharge (PT) and electrochemical impedance (EIS), and the relationship between the electrical properties and the structure of the materials was studied. The main contents and results were studied. The following are as follows: 1. MoO_2/MoS_2 electrode material was prepared by simple hydrothermal method using ammonium molybdate, sodium sodium sulfide nine and sodium borohydride to control the quality of sodium sulfide of nine water. By the structure characterization of the product, the MoO_2/ MoS_2 samples obtained by the quality of sodium sulfide of nine g have special flower like microsphere structure. The structure of rice microspheres is beneficial to the diffusion of electrolyte ions. Due to the good conductivity, special flower structure and the synergistic effect of energy storage mechanism between MoO_2 and MoS_2, the prepared MoO_2/MoS_2 electrode materials have good electrochemical performance. The specific capacity of MoO_2/MoS_2 can reach 433.3 F g-1 at the 5 mV S-1 scanning rate. After 5000 cycles, the retention rate of specific capacity was 84.41%, compared with pure MoO_2 (2000 cycles to keep 33.33%) and MoS_2 (2000 cycles to keep 58.33%) with excellent cyclic stability. Two, using ammonium molybdate, selenium powder and sodium borohydride as raw materials, MoSe_2 samples were successfully synthesized by simple hydrothermal method and subsequent heat treatment process, and MoSe_2 samples were studied. In addition, the electrochemical performance differences between the Mo elements and the MoO_2, MoS_2 and MoSe_2 three in the same main group of O, S, and Se were also investigated. The effects of the different electronegativity of the non metal elements on the electrochemical properties of the molybdenum based compound electrode materials were further investigated. MoSe_2 has unique cockscomb like structure and high conductivity. The electrochemical results show that its multiplying performance is better than that of MoO_2 and MoS_2 electrode materials. At 5 A g-1 current density, the multiplying performance can reach 75.6%.. In order to explore the device characteristics of MoSe_2, the prepared MoSe_2 is used as the negative and the self-made activated carbon (SHAC) is used as a negative electrode. Under the working window of 0~1.9 V, the MoSe_2//SHAC asymmetrical capacitor.MoSe_2//SHAC capacitor has a current density of 1 A g-1, with a specific capacity of up to 62.08 A g-1., and the energy density can reach 31.1 Wh kg-1. The cyclic stability test is carried out under the 1 A g-1 current density, and the cycle 6000 loop capacity remains 94% of the initial capacity and only attenuates. 6%. three, using sodium molybdate as raw material, deionized water as solvent, using nitric acid to regulate pH and using simple chemical precipitation method to prepare different orientations of MoO_3, the electrochemical test found that when the concentration of nitric acid is 5.2 mol L-1, MoO_3 is preferred to grow on (040) crystal surface. At the same time, the MoO_3 electrode material under this condition has excellent electrochemical properties and current density. The capacity of 1 A g-1 is up to 531.85 F g-1, and the initial capacity 96%. is kept after 3500 cycles. On this basis, MoO_3 is used as negative electrode, and the MoO_3//HNC-IPNs unsymmetrical supercapacitor is constructed with graded nano porous carbon (HNC-IPNs) as the positive pole. The capacitor exhibits excellent application characteristics under the potential window of 0~2.0 V, and is dense at 1 A g-1. Its maximum capacity is 54.72 F g-1., and its energy density and power density are better than that of AC//AC symmetric supercapacitors.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O646;TM53

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