层状过渡金属硅酸盐的合成及其析氧性能研究

发布时间：2018-03-18 03:00

本文选题：电催化析氧反应　切入点：硅酸镍钴　出处：《西华师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：化石燃料的日益短缺以及因其大量使用所带来的环境问题已经成为人类社会可持续发展的障碍。显然,有必要发掘可持续、清洁、高效的能源来取代化石燃料。氢气是一种理想的清洁能源,且电分解水制氢是未来获得高纯度氢分子的一种重要途径。析氧反应由于是多电子过程,具有缓慢的动力学和相对高的过电势,因此成为电解水的瓶颈问题。贵金属氧化物的催化效率通常可以达到要求,但高昂的价格限制了其实际应用。因此,开发价格低廉的非贵金属催化剂意义重大。层状过渡金属硅酸盐由于其独特的晶体结构,以及资源丰富、制备简单等优点已广泛应用于光学材料、催化、气体传感器和水处理剂等领域。本论文利用不同改性手段,提高了过渡金属硅酸盐电催化分解水的能力。主要研究内容如下:1、首先,用一定浓度的硝酸对多壁碳纳米管(记作MWCNTs)进行纯化处理;然后,以MWCNTs为模板,利用溶胶-凝胶法合成SiO_2并均匀负载于MWCNTs表面,得到MWCNTs@SiO_2;最后采用简单的水热反应,在180℃下反应24 h得到负载于多壁碳纳米管的碱式硅酸镍钴,即MWCNTs@(Ni,Co)_3Si_2O_5(OH)_4(记作MWCNTs@NCS)。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)等手段对其形貌、物相、组成进行分析。在0.1 M KOH电解质中对电极材料进行析氧性能测试,MWCNTs@NCS-2在10 mA·cm-2时的过电势约为440 mV,且塔菲尔斜率为96 mV/dec。MWCNTs@NCS优异的析氧性能缘于层状过渡金属硅酸盐与碳纳米管之间的协同效应。2、利用溶胶-凝胶法合成SiO_2并采用简单的水热反应得到由纳米片组成的中空微球(Ni,Co)_3Si_2O_5(OH)_4前驱体(记作NCS),再通过低温磷修饰的方法最终得到(Ni,Co)_3Si_2O_5(OH)_4-P(记作NCS-P)。改变不同的磷修饰温度以优化条件,从而探索出碱式硅酸镍钴适合磷修饰的最佳温度。通过SEM、TEM、XRD、XPS等手段对其形貌、物相、组成进行分析。在1 M KOH电解质中测试析氧性能,NCS-P-275在10 mA·cm-2时的过电势约为394 mV,且塔菲尔斜率为67 mV/dec。利用磷修饰来提高物质的电化学活性位点,从而从另外一个角度来提高过渡金属硅酸盐的电催化析氧性能。3、因为发现纯粹的碱式硅酸镍钴经过磷修饰处理后能够大大提高电催化析氧性能,我们将在第一个工作的基础上进行磷修饰,以探索性能更好的电极材料。首先,利用上述相似方法先制备负载于多壁碳纳米管上的层状碱式硅酸镍钴MWCNTs@NCS;然后,采用磷修饰的方式最终得到MWCNTs@NCS-P-400。控制实验不加次磷酸钠,其它条件(如热处理温度和时间)保持不变。通过SEM、TEM、XRD、XPS等手段对其形貌、物相、组成进行分析。在1 M KOH电解质中对电极材料进行析氧性能测试,MWCNTs@NCS-P-400在10 mA·cm-2时的过电势约为328 mV,且塔菲尔斜率为49 mV/dec。利用层状过渡金属硅酸盐与碳纳米管之间的协同效应,以及磷修饰提高物质的电化学活性位点,从而更进一步提高电催化析氧性能。
[Abstract]:The shortage of fossil fuels and because of the extensive use of the environmental problem has become the obstacle to the sustainable development of human society. It is necessary to explore, sustainable, clean, efficient energy to replace fossil fuels. Hydrogen is an ideal clean energy, electricity and water solution of hydrogen production is an important way to obtain high purity hydrogen the future of molecular oxygen evolution reaction. Because of the multi electronic process, with slow kinetics and relatively high overpotential, therefore becomes a bottleneck problem in water electrolysis. The catalytic efficiency of noble metal oxides can generally meet the requirements, but the high cost limits its practical application. Therefore, the significance of the development of non noble metal catalysts with low price layered transition metal silicate material. Because of its unique crystal structure, and is rich in resources, advantages of simple preparation, has been widely used in optical materials, catalysis, gas sensing Device and water treatment agent. Different modification methods used in this paper, to improve the ability of transition metal silicate electro catalytic decomposition of water. The main contents are as follows: 1, first of all, the multi walled carbon nanotubes with nitrate concentration (MWCNTs) was purified; then, by using MWCNTs as template. Sol gel synthesis of SiO_2 and uniform load on the surface of MWCNTs MWCNTs@SiO_2; finally, using a simple hydrothermal reaction, 24 h basic silicate nickel cobalt supported on multi walled carbon nanotubes reaction under 180 degrees, namely MWCNTs@ (Ni, Co) _3Si_2O_5 (OH) _4 (MWCNTs@NCS) by scanning. Electron microscopy (SEM), transmission electron microscopy (TEM), X ray diffraction (XRD), X ray photoelectron spectroscopy (XPS) and other means on the morphology, phase composition analysis. The oxygen evolution performance test of electrode materials in 0.1 M KOH electrolyte, MWCNTs@NCS-2 in the 10 mA - cm-2 When the potential is about 440 mV, and the Tafel slope of synergy between.2 96 mV/dec.MWCNTs@NCS with excellent performance for oxygen evolution due to layered transition metal silicate and carbon nanotubes, prepared by sol-gel method and hydrothermal reaction using SiO_2 simple hollow microspheres composed of nanosheets (Ni, Co) by _3Si_2O_5 (OH _4) precursor (NCS), to get through the method of low temperature phosphate modified (Ni, Co) _3Si_2O_5 (OH) _4-P (NCS-P). The temperature change of different phosphorus modified to optimize the conditions, in order to explore the optimum temperature of basic silicate nickel cobalt suitable phosphorus modified by SEM, TEM XRD, XPS, and other means on the morphology, phase composition analysis. The test of oxygen evolution properties in 1 M KOH electrolyte, NCS-P-275 at 10 mA over potential cm-2 is about 394 mV, and Tafel mV/dec. with a slope of 67 P modified electrochemical active sites to high material, And from another point of view to improve the electrocatalytic oxygen evolution properties of.3 transition metal silicates, because pure nickel cobalt silicate hydroxide after phosphorus after modification can greatly improve the electrocatalytic performance for oxygen evolution, we will be based on the first phosphorus modified on the electrode materials in exploring better first. First, the preparation of supported on multiwalled carbon nanotubes of layered silicate nickel cobalt hydroxide MWCNTs@NCS by using the similar method; then, using phosphorus modified MWCNTs@NCS-P-400. control experiment is obtained without the addition of sodium hypophosphite, other conditions (such as heat treatment temperature and time) remain unchanged. Through SEM, TEM, XRD, XPS etc. the morphology, phase composition analysis. To test the performance of the oxygen evolution electrode in 1 M KOH electrolyte, MWCNTs@NCS-P-400 at 10 mA over potential cm-2 is about 328 mV, and the Tafel slope is 49 mV/d Ec. utilizes the synergistic effect between layered transition metal silicates and carbon nanotubes, as well as phosphorus modification to improve the electrochemical active sites of the material, thus further improving the performance of electro catalytic oxygen evolution.

【学位授予单位】：西华师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ116.2

【参考文献】