钴基碳纳米管催化剂的构筑及在氧电极中的应用

发布时间：2018-06-26 17:32

本文选题：氧电极 + 氧还原反应　；参考：《兰州大学》2017年博士论文

【摘要】：氧电极包括两个重要的反应,即氧析出反应(OER)和氧还原反应(ORR),其效率的高低决定着许多电化学能量转换系统(如燃料电池、金属空气电池和裂解水系统)的性能。然而,这两个反应的动力学缓慢,且需依赖于贵金属催化剂(如RuO_2、IrO_2、Pt),因而极大地制约了这些技术的商业化发展。近年来,研究者们将氧电极催化剂的目光越来越多的聚集在各种以碳材料为基底的非贵金属催化剂上。本论文致力于发展高活性的钴基碳纳米管材料并将其作为氧电极催化剂,制备了几种基于碳纳米管的钴基复合纳米材料,并系统地研究了其结构特征和电化学性能。主要研究如下:1.超声辅助法快速制备CNTs-Au@Co_3O_4管状催化剂作为一种优异的电极材料用于阳极析氧通过超声法合成了均匀负载的碳纳米管/金属/过渡金属氧化物(CNTsAu@Co_3O_4)的管状杂化材料,该制备过程简单、温和、快速,且不需要加任何表面活性剂或进行热处理。在碱性介质中,CNTs-Au/Co_3O_4具有良好的析氧活性,起始电位为1.50 V _(vs).RHE,达到电流密度为10 mA cm~(-2)时的过电位为350 mV,并且可以保持至少25小时。还研究了不同电负性的金属纳米颗粒对析氧电催化活性的影响。研究结果表明,电负性最高的Au纳米颗粒可以促进活性中心Co~(IV)的形成。此外,本论文提出OER在CNTs-Au/Co_3O_4表面反应的机理。2.超薄的Co1_(-y)Fe_yO_x纳米片同轴包裹在CNTs上用于催化水氧化反应通过一步法制备了同轴包裹在CNTs上的管状铁族二元金属超薄纳米片杂化材料(Co1_(-y)Fe_yO_x/CNTs),深入讨论了催化剂的设计、制备及结构,全面分析了组分、结构、导电基底等各因素对OER活性的影响。研究表明:(1)同轴、超薄的纳米片更利于暴露活性位点、缩短扩散途径、提高接触面积;(2)Fe的掺杂会产生部分电荷转移活化(PCTA)作用,继而提高CoⅢ/CoⅣ的氧化能力,加快OER速率。在碱性溶液中,Co_(0.8)Fe_(0.2)O_x/CNTs25 wt%杂化材料表现出非常优异的OER催化活性,起始电位为1.45 V vs.RHE,塔菲尔斜率为49 mV dec-1,达到电流密度为10 mA cm-2时的过电位仅为280 mV,并且可以保持至少14小时。该催化性能优于商业的RuO_2和许多高活性的贵金属及过渡金属催化剂。3.钴的有机金属框架结构和碳纳米管的自组装杂化材料:一种高效、可抗碳腐蚀的双功能催化剂用于析氧反应和氧还原反应金属有机框架结构是由有机配体和金属离子或团簇通过配位键自组装形成的具有分子内孔隙的有机-无机杂化材料,具有丰富的骨架结构、良好的孔结构、高的比表面积和大的孔径。本论文选择了一种含钴的沸石咪唑框架结构(简称Co-MOF),并用温和的自组装法合成一种兼备高活性和强稳定性的双功能催化剂Co-MOF@CNTs用于OER和ORR反应。其中,CNTs与Co-MOF相互贯穿与支撑,不仅有效地提高了材料的导电性而且维持了材料在水氧化过程中的高氧化电位下不发生碳腐蚀。这种分层结构的杂化材料表现出与RuO_2和20 wt%Pt/C催化效果相当的OER和ORR活性和更加优异的稳定性。
[Abstract]:Oxygen electrodes include two important reactions, namely, oxygen precipitation reaction (OER) and oxygen reduction reaction (ORR), and their efficiency determines the performance of many electrochemical energy conversion systems (such as fuel cells, metal air batteries and cracking water systems). However, the kinetics of these two reactions are slow and need to be dependent on the noble metal catalysts (such as RuO_2, IrO_2, P). T), thus greatly restricts the commercialization of these technologies. In recent years, researchers have focused more and more attention on the oxygen electrode catalysts on various non precious metal catalysts based on carbon materials. This paper is devoted to the development of highly active cobalt based carbon nanotube materials and the preparation of several kinds of oxygen electrode catalysts. Carbon nanotube based cobalt based composite nanomaterials have been studied systematically and their electrochemical properties are systematically studied. The main research is as follows: 1. ultrasonic assisted preparation of CNTs-Au@Co_3O_4 tubular catalyst as an excellent electrode material is used as an excellent electrode material for the synthesis of uniform loaded carbon nanotubes / metal / transition gold by ultrasonic method. The tubular hybrid material of the oxide (CNTsAu@Co_3O_4) is simple, mild and fast, without any surface active agent or heat treatment. In the alkaline medium, CNTs-Au/Co_3O_4 has good oxygen evolution activity and the starting potential is 1.50 V vs.RHE, and the overpotential at the current density of 10 mA cm~ (-2) is 350 mV, and The effect of different electronegativity metal nanoparticles on the electrocatalytic activity of oxygen evolution was also studied. The results showed that the highest electronegativity Au nanoparticles could promote the formation of active center Co~ (IV). In addition, this paper proposed that the mechanism of OER on CNTs-Au/Co_3O_4 surface reaction is.2. ultra-thin Co1_ (-y) Fe_yO_x Nana. A tube shaped iron group of two yuan metal super thin nano chip hybrid material (Co1_ (-y) Fe_yO_x/CNTs) coaxially wrapped in CNTs was prepared by one step method for the catalytic water oxidation of rice on CNTs. The design, preparation and structure of the catalyst were discussed in depth. The effects of components, structure and conductive substrate on the activity of OER were analyzed. Research shows that (1) (1) coaxial, ultra-thin nanoscale is more conducive to exposure to active sites, shorten the diffusion pathway and increase contact area; (2) the doping of Fe will produce partial charge transfer activation (PCTA), and then increase the oxidation capacity of Co III /Co IV and accelerate the OER rate. In alkaline solution, Co_ (0.8) Fe_ (0.2) O_x/CNTs25 wt% hybrid material shows non The often excellent OER catalytic activity, the starting potential of 1.45 V vs.RHE, and the Tafel slope of 49 mV dec-1, is only 280 mV when the current density is 10 mA cm-2, and can remain at least 14 hours. The catalytic performance is superior to the commercial RuO_2 and many highly active precious metals and the transition metal catalysts for the organometallic framework of.3. cobalt. A self assembled hybrid material for carbon nanotubes: a highly efficient, carbon resistant, bifunctional catalyst used in oxygen evolution and oxygen reduction. The organic frame structure is an organic inorganic hybrid material composed of organic ligands and metal ions or clusters formed by self assembly through the coordination bonds. It has a rich skeleton. The structure, good pore structure, high specific surface area and large aperture. In this paper, a cobalt containing zeolite imidazole frame structure (Co-MOF) was selected, and a dual functional catalyst, Co-MOF@CNTs, which had both high activity and strong stability, was synthesized by a mild self-assembly method for the reaction of OER and ORR. Among them, CNTs and Co-MOF were interpenetrated and supported, It not only effectively improves the conductivity of the material but also maintains the material without carbon corrosion under the high oxidation potential in the process of water oxidation. This layered hybrid material shows the activity of OER and ORR, which is equivalent to the catalytic effect of RuO_2 and 20 wt%Pt/C, and the more excellent stability.
【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O646;O643.36

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