三维纳米网状Mn基氧化物的孔径及其电化学性能研究

发布时间：2018-05-06 18:20

本文选题：阳极电沉积 + Mn氧化物　；参考：《南昌航空大学》2015年硕士论文

【摘要】：针对MnO2存在导电性差、真实比容低、离子传导性差等问题,本文开发了新的制备方法和掺杂改性工艺,制备出了三维纳米网状结构的Mn基氧化物。本论文采用阳极电沉积的方法制备具有三维纳米网状结构的MnO2和MnVFe氧化物,并系统研究了工艺参数、元素掺杂等因素对锰基氧化物纳米结构及性能的影响,并利用X射线衍射仪(XRD)、场发射扫描电镜(FESEM)、能谱仪(EDS)等检测技术及电化学测试方法对锰基氧化物的结构和性能进行了表征。研究表明,采用恒电流脉冲电沉积制备三维多孔MnO2材料,电流密度和通断比各为0.435 mA/cm2、7:1和0.87 mA/cm2、10:1时,都能获得由纳米线自组装成的三维网状,孔径约40 nm;电流密度和通断比为0.435 mA/cm2、10:1时,可获得近乎垂直于基底的相互交织的开放式纳米片薄膜;电流密度和通断比为0.87 mA/cm2、15:1时,形成了细小密集纳米片,并互相交织形成三维多孔结构,孔径约200nm。采用恒电位脉冲电沉积制备三维多孔MnO2材料,通断比都为3:1,沉积电位0.9 V时,制备的薄膜形成了由直径约50 nm、长度约200 nm的纳米线自组装成的三维孔结构;沉积电位1 V时,制备的薄膜表面及截面均为三维网状结构。阳极电沉积电流密度为5~200 m A·cm2时,形成由直径约3~80 nm、长径比约5~10的纳米线自组装成的三维纳米网状结构,网孔分布均匀。重点考察电流密度、NaVO3浓度、NH4Fe(SO4)2浓度和PH值四个因素,设计正交实验,采用阳极电沉积法制备的MnVFe氧化物基本都具有三维纳米网状结构,孔径约3~80 nm,具有典型的γ-MnO2晶体相结构。根据正交试验结果选出了4种具有不同网孔孔径的MnVFe氧化物,孔径分布范围分别为3~10 nm、15~40 nm、40~60 nm和60~80 nm,研究了扫描速度对不同孔径MnVFe氧化物电容性能的影响。扫描速率为0.5mV/s时,不同孔径各自的比容量分别为450.91F/g、398.55 F/g、289.15 F/g和253.17 F/g;充放电速率为0.2A/g时,不同孔径各自的比容量分别为475.25 F/g、428.5 F/g、328.75 F/g和312.86 F/g。扫描速率由0.5mV/s增大至200 mV/s时,4种不同孔径的MnVFe氧化物的比电容保持率分别35%、54%、60.2%和36.7%;充放电速率由0.5 A/g增大至5 A/g时,4种不同孔径的MnVFe氧化物的比电容保持率分别69%、81%、86%和72%。与未掺杂的MnO2相比,MnVFe氧化物细小的三维纳米网状结构极大增加了电极的导电性,其比容量提高36%。在不同浓度的Na2SO4电解液中,扫描速率为1A/g时,MnVFe氧化物的比电容在浓度为0.5 mol/L时最大,可达253.4 F/g。
[Abstract]:In order to solve the problems of poor electrical conductivity, low real specific volume and poor ionic conductivity in MnO2, a new preparation method and doping modification technology were developed to prepare Mn-based oxides with three-dimensional nanoscale structure. In this paper, MnO2 and MnVFe oxides with three dimensional nanocrystalline meshes were prepared by anodic electrodeposition, and the effects of process parameters and element doping on the structure and properties of manganese based oxides were studied systematically. The structure and properties of manganese based oxides were characterized by X-ray diffractometer (XRD), field emission scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The results show that when the current density and the on-to-break ratio are 0.435 Ma / cm _ 2 / 7: 1 and 0.87 Ma / cm _ 2 / 10: 1, respectively, the three-dimensional porous MnO2 materials prepared by constant current pulse electrodeposition can be self-assembled by nanowires. When the current density and the on-to-break ratio are 0.435 Ma / cm ~ (2) 10: 1, the interlaced open nanocrystalline films almost perpendicular to the substrate can be obtained. When the current density and the on-to-break ratio are 0.87 Ma / cm ~ (2) / 15: 1, small and dense nanocrystals are formed. And intertwined with each other to form a three-dimensional porous structure with a pore size of about 200 nm. Three-dimensional porous MnO2 materials were prepared by potentiostatic pulse electrodeposition with a ratio of 3: 1 and a potential of 0.9 V. The films were self-assembled by nanowires of about 50 nm in diameter and 200 nm in length, and the deposition potential was 1 V. The surface and cross section of the prepared films are all three-dimensional reticulated structures. When the current density of anodic electrodeposition is 5 ~ 200mA cm2, a three-dimensional nanowire structure is formed by self-assembly of nanowires with a diameter of about 3nm and a aspect ratio of about 5 ~ 10, and the net pores are uniformly distributed. Four factors, NH _ 4Feo _ 4SO _ 4 concentration and PH value of NaVO3 concentration, were investigated in detail. Orthogonal experiment was designed. The MnVFe oxides prepared by anodic electrodeposition all had three-dimensional nano-network structure, pore size about 380nm, and typical 纬 -MnO _ 2 crystal phase structure. According to the results of orthogonal experiments, four kinds of MnVFe oxides with different pore sizes were selected. The pore size distribution ranges from 3 ~ 10 nm to 1540 nm ~ 40 nm ~ 4060 nm and 60 ~ (80) nm, respectively. The effect of scanning speed on the capacitance of MnVFe oxides with different pore sizes was studied. When the scanning rate is 0.5mV/s, the specific capacity of different aperture is 450.91F / g 398.55F / g 289.15F / g and 253.17 Fr / g, respectively. When the charge / discharge rate is 0.2A/g, the specific capacity of different aperture is 475.25 F / g 428.5 FG 328.75 FG and 312.86 Fr / g respectively. The specific capacitance retention rates of the four kinds of MnVFe oxides with different pore sizes increased from 0.5mV/s to 200 mV/s, and the specific capacitance retention rates of the four MnVFe oxides with different apertures were 6981 86% and 722%, respectively, when the charge / discharge rate increased from 0.5 Ag to 5 Ag, and the specific capacitance retention rates of the four MnVFe oxides with different pore sizes were 540.2% and 36.7%, respectively, and the charge-discharge rate increased from 0.5 Ag to 5 Ag. Compared with the unadulterated MnO2, the electrical conductivity and the specific capacity of the electrode are increased by 36%. In different concentration of Na2SO4 electrolyte, the specific capacitance of Mn-MnVFe oxides can reach 253.4 F / g at the concentration of 0.5 mol/L when the scanning rate is 1A/g.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ137.12;TB383.1

【共引文献】