源于丝瓜络的巨孔碳及其复合材料的制备与电化学性能

发布时间：2018-01-08 20:13

本文关键词：源于丝瓜络的巨孔碳及其复合材料的制备与电化学性能　出处：《哈尔滨工业大学》2015年博士论文　论文类型：学位论文

【摘要】：面对化石能源的日益枯竭及其所带来的环境问题,可再生清洁能源的开发和利用日益迫切,在众多的能源器件中超级电容器和燃料电池由于其突出优点而备受关注。超级电容器具有充放电速度快、循环寿命长、成本低廉等优点,目前超级电容器作为储能器件的主要问题是其能量密度低,提高其能量密度的主要途径是制备高性能的电极材料。燃料电池具有转换效率高、排放低、燃料来源丰富等优点,目前阻碍燃料电池应用的主要因素之一是其所使用的铂催化剂成本过高,因此,研发廉价的高性能非贵金属催化剂对燃料电池的应用是一个紧迫问题。本论文面向超级电容器和燃料电池应用所存在的问题采用丝瓜络为前驱体制备了巨孔碳,并在巨孔内表面生长了MnO_2纳米片、过渡金属离子掺杂的MnO_2纳米片和聚苯胺(PANI)纳米线,成功获得了活性材料在巨孔碳内表面生长的复合材料,研究了巨孔碳及复合材料的超级电容和氧还原催化性质。主要研究内容和结果如下:以丝瓜络为前驱体,采用在NH_3中高温碳化并在N2中活化的工艺制备了巨孔碳。巨孔碳继承了丝瓜络纤维的巨孔结构,即每一根碳纤维都包含密集平行排列的孔道,孔道直径为4-10mm,壁厚为0.3-1mm。其内壁活化后产生了大量的微孔和介孔,形成一个具有多层次的孔结构,其比表面积最高达到1678.1m2/g。由于电解质能够通过巨孔进入巨孔碳的内部,使电极材料的利用率得到有效地提高。研究发现,将巨孔碳用作超级电容器材料时在Na2SO4、KOH、H2SO4的水系电解液中,在1A/g的充放电电流密度下比电容分别为167、196和249F/g,而且巨孔碳拥有良好的循环稳定性,在上述三种电解液中经过5000次循环后其电容保持率分别为95.7%、95.0%和87.6%。巨孔碳用作氧还原反应的催化剂时具有良好的催化活性,在KOH和H2SO4电解液中的氧还原峰电位分别为-0.10V和0.32V,峰电流密度分别为0.27 m A/cm~2和0.26m A/cm~2,起始电位分别为0.00V和0.51V。由于巨孔碳大部分的活性点在孔道的内表面,避免了材料在使用过程中因团聚而产生的性能衰退现象。稳定性测试表明,经过12h,电流强度在KOH和H2SO4的电解液中的保持率分别为81.3%和88.5%,在酸性介质中的稳定性尤其突出。通过与高锰酸钾溶液反应在巨孔碳内表面生长了MnO_2纳米片,由于巨孔碳的大孔径实现了纳米片在内表面上的全覆盖生长。由于电解液能够借助巨孔进入到材料的内部,使内表面生长的MnO_2纳米片与电解液充分接触,MnO_2纳米片在高载量的条件下仍具有很高的质量比电容。研究表明,在MnO_2的载量为0.15、2.15和5.69mg/cm~2时,纯MnO_2纳米片的质量比电容分别为1332、567和354F/g。另外,电极材料在高载量时也具很高的面电容,当MnO_2纳米片载量为5.69mg/cm~2时,活性材料的面电容可达2.9F/cm~2。以MnO_2和巨孔碳的复合材料为电极材料组装成对称超级电容器,在面功率密度为4.5mW/cm~2时面能量密度可达194mWh/cm~2,在电流密度为5m A/cm~2时,经过5000次充放电循环后电容的保持率为80%。为了进一步提高MnO_2纳米片的超级电容性能和氧还原催化活性,通过在反应溶液中加入相应的金属盐,实现了室温下在巨孔碳的内表面生成了金属离子掺杂的MnO_2纳米片。系统地研究了掺杂金属离子的种类对MnO_2纳米片的超级电容性能和氧还原催化活性的影响。研究表明,作为超级电容器材料时,Ni离子掺杂的MnO_2纳米片的性能最好,在电流密度1A/g时比电容为445F/g(基于MnO_2和巨孔碳的总质量),并且具有良好的循环稳定性,经过1000次充放电后,其电容保持率为90%。作为ORR催化剂时,Co离子掺杂的MnO_2纳米片的性能最佳,反应峰电位、峰电流、起始电位和电子转移数分别为-0.13V、0.37m A/cm~2、-0.04V和3.64。经过12小时的稳定性测试,Co离子掺杂的MnO_2纳米片的电流稳定在初始值的86.9%,优于未掺杂的MnO_2纳米片。利用原位聚合法在巨孔碳的内表面生长了垂直定向的聚苯胺纳米线。研究发现,苯胺浓度对聚苯胺的形貌有重要影响,通过选择合适的浓度获得垂直于巨孔碳壁面定向生长的聚苯胺纳米线。由于孔道内表面的聚苯胺能够完全暴露于电解液中,聚苯胺的利用率得到极大的提高,在1A/g的电流密度下,聚苯胺的比电容高达1500F/g。同时巨孔结构有利于电解液输运,当电流密度增加到10A/g时比电容仍保持为原来的70%,具有良好的倍率性能。以PANI和巨孔碳的复合材料为电极材料组装成的对称电容器在功率密度为0.5k W/kg时的能量密度为19Wh/kg,在2A/g的电流密度下经过7000次循环,其比电容为原来的83%,具有良好的循环稳定性。
[Abstract]:In the face of environmental problems the depletion of fossil energy and the development and utilization of clean energy, renewable energy has become increasingly urgent, in the numerous devices of super capacitor and fuel cell due to its outstanding advantages and concern. Super capacitor with fast charge and discharge, long cycle life, low cost and other advantages, the main problems at present the super capacitor as the energy storage device is its low energy density, the main way to improve the energy density of the electrode material is prepared with high performance. The fuel cell has high conversion efficiency, low emissions, abundant fuel source etc., one of the main factors that currently impede fuel cell applications is the use of the platinum catalyst cost is too high therefore, the development of low-cost, high performance non noble metal catalysts for fuel cell applications is an urgent problem. This paper for super capacitor and fuel cell applications The problems of preparation of mesoporous carbon as precursor by giant loofah, and the giant hole surface growth of nano MnO_2, nano MnO_2 and polyaniline doped with transition metal ions (PANI) nanowires, successfully obtained composite material surface active material in megaporous carbon growth within the research giant mesoporous carbon composite material and the super capacitor and the oxygen reduction catalytic properties. The main research contents and results are as follows: Loofah as precursor, giant hole carbon fabricated by high temperature carbonization and activation in NH_3 in N2. The giant giant inherited the pore structure of porous carbon fiber loofah, every carbon fiber contains dense and parallel arrangement of the pore, the pore diameter is 4-10mm, thickness of the inner wall of 0.3-1mm. after activation produced a large number of micropores and mesopores, has formed a multi-level pore structure, the surface area of up to 1678.1m2/g. as the electrolyte Inside the hole into the hole enough through the giant giant carbon electrode materials, the rate has been effectively improved. The study found that the giant hole carbon as super capacitor materials in Na2SO4, KOH, H2SO4 aqueous solution, the charge discharge current density of 1A/g capacitance is 167196 and 249F/g respectively, and the giant carbon have good cycle stability. After 5000 cycles of the three kinds of electrolyte and its capacitance retention rate was 95.7%, the catalyst has good catalytic activity for oxygen reduction reaction and 95% 87.6%. carbon is used as the giant hole, KOH and H2SO4 in the electrolyte in the oxygen reduction peak potential were -0.10V and 0.32V. The peak current density was 0.27 M A/cm~2 and 0.26M A/cm~2, respectively 0.00V and 0.51V. initial potential due to the giant hole in most of the active carbon in surface pore, avoid the properties of materials in the use of the process for the reunion time Withdrawal phenomenon. The stability test showed that after 12h, the strength of the current in the electrolyte KOH and H2SO4 in keeping rates were 81.3% and 88.5%, stability in acid medium. Especially by reaction with Potassium Permanganate in a giant hole in the surface of the carbon solution growth of MnO_2 nano films, due to the large aperture megaporous achieved nano carbon on the inner surface of the sheet covering the whole growth. Because the electrolyte can help megaporous into the internal material, the nano MnO_2 and electrolyte surface growth of full contact, the MnO_2 nanosheets in high load conditions the quality still has a high specific capacitance. The results show that the loading of MnO_2 is 0.15,2.15 and 5.69mg/cm~2, the quality of pure nano MnO_2 specific capacitance were 1332567 and 354F/g. respectively. In addition, the electrode material with high surface capacitance in high load, when the nano MnO_2 load is 5.69mg/cm~2, the surface active material Capacitance of composite material MnO_2 and 2.9F/cm~2. to the giant hole carbon electrode material for super capacitor assembled into a symmetrical, in the face of power density is 4.5mW/cm~2 when the surface energy density of 194mWh/cm~2, the current density of 5m A/cm~2, after 5000 cycles the capacitance retention rate of 80%. in order to further improve the performance of supercapacitor and oxygen the catalytic activity of nano MnO_2, by adding the corresponding metal salt in the reaction solution, realized at room temperature on the inner surface of the giant hole generated carbon nano MnO_2 doped with metal ions. Studied the performance of supercapacitor and oxygen species of metal ion doping on nano MnO_2 reduction of catalytic activity. The results show that as the supercapacitor materials, properties of MnO_2 nanosheets doped Ni best, at the current density of 1A/g specific capacitance is 445F/g (based on MnO_2 and the giant hole carbon Total quality), and has good cycle stability. After 1000 cycles, the capacitance retention rate of 90%. ORR as catalyst, Co doped MnO_2 nanosheets with the best performance, response peak potential, peak current, initial voltage and electron transfer number were -0.13V, 0.37M, A/cm~2, -0.04V and 3.64. after the stability test for 12 hours, Co ion doped MnO_2 nanosheets with stable current at the initial value of 86.9%, better than the undoped MnO_2 nanosheets. Polyaniline nanowires vertically oriented growth on the inner surface of the giant hole carbon by in situ polymerization. The study found that the concentration of aniline has an important influence on the polyaniline morphology, obtain perpendicular to the giant hole wall carbon directional growth of polyaniline nanowires by choosing appropriate concentration. Because the pore surface of polyaniline can be exposed in the electrolyte, the utilization rate of polyaniline to greatly improve In the high current density of 1A/g, the specific capacitance of polyaniline 1500F/g. and giant pore structure facilitates the electrolyte transport, when the current density increased to 10A/g the specific capacitance retained 70% of the original, with good rate capability. The PANI composite material and the giant porous carbon for the symmetric capacitor electrode assembly at a power density of 0.5K W/kg when the energy density is 19Wh/kg, the current density of 2A/g after 7000 cycles, the specific capacitance is 83% of the original, has a good cycle stability.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB33

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