基于钴纳米晶的高性能电化学催化剂的制备及电解水性能的研究

发布时间：2017-12-28 21:27

本文关键词：基于钴纳米晶的高性能电化学催化剂的制备及电解水性能的研究　出处：《中国科学技术大学》2017年博士论文　论文类型：学位论文

【摘要】：随着经济和社会的飞速发展,能源问题越来越成为世界性的难题之一,氢能源作为重要的新能源一直受到广泛的关注,氢气可以作为零碳源的清洁能源直接燃烧,而且可以把别的清洁能源转化成氢气储备或运输。氢气的制备方法有很多,其中电解水制备氢气是最简单最清洁的方法,但是直接电解水的能垒比较高,因此需要研究开发合适的电化学催化剂以降低电解水的能垒,加速氢气的产生。众所周知,以铂为代表的贵金属材料是高性能的电解水催化剂,但贵金属储量稀少、价格昂贵,直接制约了其在催化电解水制备氢气领域的广泛应用,所以研究开发基于非贵金属材料的电解水催化剂十分必要。钴作为地壳含量丰富且高导电性的过渡金属元素,其单质及化合物已经在催化电解水产氢或产氧领域有很广泛的研究,但其催化性能与贵金属材料相比还有较大的差距。本论文的主要内容是设计合成由钴纳米晶组装成的纳米空心球状和纳米片状催化剂,并研究这些具有特定形貌和结构的电化学催化剂在碱性或者中性溶液中催化电解水的性能。本论文主要包括以下内容:第一章是绪论,我们详细介绍了电解水制备氢气的历史和意义,以及氢电极和氧电极上反应的类型和基本原理,然后我们分别介绍了不同结构形貌的钴基产氢反应催化剂和产氧反应催化剂,以及设计合成这些催化剂时依据的不同条件,最后我们介绍了基于不同催化剂的电解池,以及双功能催化剂组成电解池体系,这些电解池可以与光电池串联起来,实现了光能转换成氢能储存。在第二章中,我们通过化学还原的方法合成了由钴纳米晶组装的纳米空心球,作为高性能的产氢反应催化剂。纳米空心球结构具有很高的比表面积,可以充分发挥钴纳米晶作为活性中心的作用,非晶态的氧化物层既保护钴纳米晶不被氧化,又支撑空心球的结构,使催化剂表现出优异的稳定性。在中性溶液中,这种纳米空心球结构的催化剂表现出良好的催化活性和优异的稳定性。我们的研究结果表明,制备由非贵金属纳米晶组装成的具有中空结构的催化剂是研究开发高性能电催化剂的一个很有前景的方向。在第三章中,我们采用两种不同的合成方法得到两种钴基非晶态合金材料,将这两种材料作为前驱体在镍泡沫电极上进行原位的电化学活化,分别得到具有纳米片阵列结构的氢电极和氧电极。其中,氢电极是先通过原位电沉积的方法在镍泡沫电极上沉积钴合金作为前驱体,在碱性溶液中进行电化学还原活化后,就得到有优越的产氢活性和高稳定性的钴金属纳米片阵列,在碱性溶液中的产氢活性优于贵金属Pt/C。氧电极是先通过化学还原的方法得到钴-铁-硼合金作为前驱体,然后负载在镍泡沫电极上并进行电化学氧化活化,得到钴-铁-硼氧化物纳米片阵列,其在碱性溶液中的产氧活性优于贵金属IrO2。将这两个钴基氢电极和氧电极组装成电解池,其电解水性能优于贵金属催化剂组成的电解池Pt/C ‖ IrO2。我们的研究结果表明,由原位电化学活化得到的纳米片阵列结构具有高比表面积,同时纳米片和基底之间的接触电阻小,所得钴基纳米片阵列的催化电解水活性和稳定性大幅度超过贵金属催化剂。由于这类钴基纳米片催化剂的制备非常简单,并且性能优异,所以具有广泛的应用前景。第四章中,我们将负载非贵金属合金前驱体的镍泡沫在碱性溶液中进行电化学还原活化,得到低氧化态的钴-铁-钨-硼四元合金纳米片阵列催化剂,该催化剂在中性溶液中电解水产氢的活性优于前面合成的钴纳米晶空心球催化剂,非常接近Pt/C在相同条件下的催化性能。另一方面,将负载了非贵金属合金前驱体的镍泡沫进行电化学氧化活化,得到高氧化态的钴-铁-钨-硼氧化物纳米片阵列,该催化剂在中性溶液中电解水产氧的活性优于贵金属IrO2。将这两个基于钴-铁-钨-硼纳米片阵列的电极组成使用中性电解液的电解池,其电解水的性能优于贵金属组成的电解池(Pt/C ‖ IrO2)。我们的研究结果为设计制备中性溶液中的催化电解水的高性能催化剂提供了一个非常简单高效的方向,可以进一步的降低电解水制备氢气的成本。
[Abstract]:With the rapid development of economy and society, the energy problem is becoming one of the world's problem, the hydrogen energy as important new energy has attracted extensive attention, hydrogen can be directly burned as zero carbon source of clean energy, but also can make the other clean energy into hydrogen storage or transportation. There are many ways to prepare hydrogen. The electrolysis of water to prepare hydrogen is the simplest and cleanest way, but the energy barrier of direct electrolysis is relatively high. Therefore, it is necessary to research and develop suitable electrochemical catalysts to reduce the barrier of electrolyzed water and accelerate the generation of hydrogen. As everyone knows, the precious metal materials to platinum is water electrolysis catalysts with high performance, but the precious metal reserves are scarce and expensive, directly restricts its wide application in catalytic water electrolysis hydrogen preparation field, so the research and development of water electrolysis of non noble metal materials based on the catalyst is necessary. Cobalt as a transition metal element with high content and high conductivity in the earth's crust has been extensively studied in the field of catalytic electrolysis of hydrogen and oxygen production, but its catalytic performance is far from that of precious metal materials. The main content of this paper is to design and synthesize nano hollow spherical and nanoscale catalysts assembled from cobalt nanocrystals, and study the catalytic performance of these specific catalysts with specific morphology and structure in the electrolysis of water in alkaline or neutral solutions. This paper mainly includes the following contents: the first chapter is the introduction, we introduce the history and significance of the preparation of electrolyzed water hydrogen hydrogen, and the type of electrode and the oxygen electrode reaction and the basic principle, then we introduce the cobalt based hydrogen production catalyst with different structure and morphology of oxygen producing catalyst, and different the design and synthesis of these catalysts according to conditions, finally we introduce the electrolytic cell of different catalysts based on bifunctional catalyst composition and electrolytic cell system, the electrolytic cell can connect with the light battery, realize the conversion of light energy into hydrogen storage. In the second chapter, we synthesized nanosized hollow spheres composed of cobalt nanocrystals by chemical reduction as a high performance catalyst for hydrogen production. Nano hollow spheres have high specific surface area, which can give full play to the role of cobalt nanocrystals as active centers. The amorphous oxide layer not only protects cobalt nanocrystals from being oxidized, but also supports the structure of hollow spheres, so that the catalysts exhibit excellent stability. In the neutral solution, the catalyst of the nanohollow sphere structure shows good catalytic activity and excellent stability. Our research results show that the preparation of catalysts with hollow structure assembled from non noble metal nanocrystals is a promising direction to research and develop high performance electrocatalysts. In the third chapter, we use two different synthesis methods to get two kinds of cobalt based amorphous alloy materials. These two materials are used as precursors in situ electrochemical activation of nickel foam electrodes, and hydrogen and oxygen electrodes with nano array structure are obtained respectively. Among them, the hydrogen electrode is first deposited by in situ deposition on nickel foam electrode cobalt alloy as precursor, electrochemical reduction activation in alkaline solution, get the superior hydrogen production activity and cobalt metal nano film high stability array, hydrogen production activity is better than that of noble metal Pt/C in alkaline solution. The oxygen electrode is first obtained by chemical reduction. The cobalt iron boron alloy is used as precursor, then loaded on the nickel foam electrode and activated by electrochemical oxidation. The cobalt iron boron oxide nanosheet array is obtained. Its oxygen production activity in alkaline solution is better than that of noble metal IrO2. The two cobalt based hydrogen electrode and the oxygen electrode assembly into the electrolytic cell, the electrolysis of water is better than precious metal catalyst Pt/C / / IrO2 electrolytic cell. Our results show that, by in situ electrochemical activation of nanosheets structure with high specific surface area, and the contact resistance between the nano film and substrate, greatly the catalytic activity and stability of the water electrolytic cobalt base nanosheets over noble metal catalysts. Because of its very simple preparation and excellent performance, this kind of cobalt based nanoscale catalyst has a wide application prospect. In the fourth chapter, we will load nickel foam non noble metal alloy precursor for electrochemical reductive activation in alkaline solution, low oxidation state of cobalt iron tungsten alloy element boron four nanosheets catalyst activity than the catalyst in neutral solution electrolytic hydrogen before the synthesis of cobalt nanocrystals hollow spherical catalyst, the catalytic performance is very close to the Pt/C in the same conditions. On the other hand, the nickel foam loaded with non noble metal precursor was activated by electrochemical oxidation to obtain the cobalt oxide iron tungsten oxide nanosheet array with high oxidation state. The activity of the catalyst in the neutral solution is better than that of the noble metal IrO2. The two electrode electrolytic cell based on cobalt - iron - boron tungsten nanosheets composed using neutral electrolyte, electrolytic cell composition of electrolytic water is better than precious metals (Pt/C, IrO2). Our results provide a very simple and efficient way to design and prepare high-performance catalysts for the catalytic electrolysis of water in neutral solutions, which can further reduce the cost of electrolysis of water to prepare hydrogen.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36;TQ116.21

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