卟啉基非贵金属仿生氧还原催化剂的制备及应用

发布时间：2018-06-18 11:12

本文选题：卟啉 + 基非　；参考：《吉林大学》2015年博士论文

【摘要】：随着能源危机日趋严重,人们对直接甲醇燃料电池(Direct Methanol Fuel Cell,DMFC)和微生物燃料电池(Microbial Fuel Cell,MFC)进行了广泛研究,而制约这两种电池技术广泛应用的主要瓶颈之一是其阴极氧还原反应的催化剂。目前,最常用的阴极催化剂是铂基催化剂,但铂基催化剂较为昂贵,且容易中毒。因此,开发廉价且高效的非贵金属替代催化剂已成为燃料电池和微生物燃料电池研究和应用的一个重要科学问题,具有重要的研究意义。自然界辅酶和辅基的催化中心结构为氧还原反应催化剂的开发提供了重要启示。这些辅酶和辅基通常具有铁卟啉或钴卟啉配合中心,在生物体内的氧气运载和多种氧化还原反应中发挥重要作用。受此启发,人们广泛研究了非贵金属大环配合物的氧还原催化性能,研究较多的非贵金属包括铁、钴等,而配位大环则多是卟啉、酞菁及其衍生物。但此类离散的配合物在电解质溶液中容易解离,不利于电池的长期稳定运行。为进一步提高非贵金属大环配合物催化剂在溶液中的稳定性,人们构建了嵌入多金属中心的共价有机框架。共价有机框架(Covalent Organic Frameworks)是一类相对有序的共价有机聚合物(Covalent Organic Polymers),具有多孔的有序结构和良好的稳定性,因此,基于共价有机框架的多金属中心催化材料已成为近期氧还原催化剂研究的热点。本文基于空气阴极直接甲醇燃料电池和微生物燃料电池等应用背景,针对氧还原催化剂研究中的重要科学问题,利用师法自然的仿生思想,借鉴自然界辅酶和辅基的中心结构,制备了嵌入非贵金属有机大环分子配合中心的二维和三维共价有机框架,对其进行了物理化学表征和电化学测试,并将部分材料应用于微生物燃料电池。主要工作和研究结论如下:1.首次通过炔烃复分解反应合成了一种共轭多孔的二维钴卟啉基有机框架材料(Co PEF),并将廉价的碳黑作为电子导体与Co PEF进行混合,将混合物(Co PEF/C)作为氧还原催化剂。无论是在酸性还是碱性介质中,Co PEF/C均表现出了良好的氧还原催化性能。相比于钴卟啉单体,共轭的框架材料增强了氧还原的催化活性,具体表现为更高(更正)的初始电势和更大的限制电流密度。这可能是由于Co PEF的多孔性和共轭性使活性位点更充分暴露,并利于更有效的电子与物质传递。催化机理研究发现Co PEF/C催化下的氧还原反应主要通过4电子催化途径,产物接近于全部为水。此外,相对于钴卟啉单体和商用催化剂Pt/C,Co PEF/C还兼具更加良好的稳定性和甲醇耐受性。2.基于二维钴卟啉基有机框架材料(Co PEF),开发了一种多孔、高比表面积的三维钴卟啉基有机框架材料(Co POP),并将其应用于氧还原催化。Co POP在酸性和碱性介质中均显示出了优异的稳定性,持续工作50000秒时催化电流基本没有变化。该材料热解后的稳定性和比表面积虽有所下降,但氧还原催化活性却有所提升。TEM,HRTEM,XPS和XRD等一系列表征发现热解后的材料是包裹着钴纳米粒子的掺氮碳材料。电化学测试表明最优的热解温度为800°C,所得的材料(Co POP-800)具有最高的催化活性,其催化性能和商用Pt/C相比,相近、甚至更优。另外,Co POP-800/C催化的氧还原为4电子催化机理,将氧气直接还原成水,且Co POP-800/C还具有非常优异的甲醇耐受性和稳定性。3.通过热解一种新型多孔、高比表面积的铁卟啉基高分子材料获得了Fe-Nx/C催化剂,并将其应用于单室微生物燃料电池的空气阴极。在中性介质中,Fe-Nx/C展现出良好的氧还原催化性能。这可能是因为铁基纳米粒子和掺氮的石墨碳层产生了协同催化作用。此外,相对于Pt/C阴极的微生物燃料电池,Fe-Nx/C阴极的微生物燃料电池展示出了更加优异的性能,具体表现在更佳的电池电压、最大功率密度和库伦效率。这些研究表明Fe-Nx/C比Pt/C能更加适应和耐受具有细菌的微生物燃料电池体系,进而具有更好的实用前景。
[Abstract]:As the energy crisis is getting worse, people have studied the direct methanol fuel cell (Direct Methanol Fuel Cell, DMFC) and microbial fuel cell (Microbial Fuel Cell, MFC), and one of the main bottlenecks that restricts the wide application of these two battery technologies is the catalyst for the negative oxygen reduction reaction. Chemical agents are platinum based catalysts, but platinum based catalysts are more expensive and easy to be poisoned. Therefore, the development of cheap and efficient non noble metal substitutive catalysts has become an important scientific problem in the research and application of fuel cells and microbial fuel cells. The development of the reduction reaction catalyst provides important inspiration. These coenzymes and cofactors usually have iron porphyrin or cobalt porphyrin, which play an important role in oxygen delivery and redox reactions in organisms. Inspired by this, people have extensively studied the catalytic performance of oxygen reduction of non precious metal macrocyclic complexes, and more research has been made. Non precious metals include iron and cobalt, while large rings are mostly porphyrin, phthalocyanine and their derivatives. But such discrete complexes are easily dissociated in electrolyte solutions and are not conducive to the long-term stable operation of the batteries. In order to further improve the stability of the catalyst in the solution of non precious metal macrocyclic complexes, a multi metal center is built. Covalent organic frame. The covalent organic framework (Covalent Organic Frameworks) is a kind of relatively ordered covalent organic polymer (Covalent Organic Polymers), which has porous structure and good stability. Therefore, the multi metal center accelerating material based on covalent organic frame has become a hot spot in the recent study of oxygen reduction catalyst. Based on the application background of the air cathode direct methanol fuel cell and the microbial fuel cell, this paper aims at the important scientific problems in the study of the oxygen reduction catalyst. By using the natural bionic idea of the teacher's method and drawing on the central structure of the natural coenzyme and auxiliary base in nature, the two-dimensional and three-dimensional structure of the organic macrocyclic molecular coordination center of the non precious gold genus is prepared. The covalent organic framework was used for physical and chemical characterization and electrochemical testing, and some materials were applied to microbial fuel cells. The main work and research conclusions are as follows: 1. a conjugated porous two-dimensional cobalt porphyrin organic frame material (Co PEF) was synthesized by the complex decomposition reaction of alkynes for the first time, and the cheap carbon black was used as the electron. The conductor is mixed with Co PEF, and the mixture (Co PEF/C) is used as an oxygen reduction catalyst. Both in acid or alkaline medium, Co PEF/C shows good catalytic performance in oxygen reduction. The conjugate frame material increases the catalytic activity of oxygen reduction compared to the cobalt porphyrin monomer. This may be due to the porosity and conjugation of Co PEF, which makes the active sites more fully exposed and is beneficial to the more effective electron and material transfer. The catalytic mechanism studies found that the oxygen reduction reaction under the catalysis of Co PEF/C is mainly through 4 electron catalysis, the product is nearly all water. In addition, relative to the cobalt porphyrin monomer. The commercial catalyst Pt/C, Co PEF/C also have a better stability and methanol tolerance.2. based on the two-dimensional cobalt porphyrin based organic frame material (Co PEF). A three-dimensional cobalt porphyrin based organic frame material (Co POP) with porous, high specific surface area (Co POP) has been developed and applied to the oxygen reduction catalyst.Co POP in both acidic and alkaline media. The catalytic current was basically unchanged at 50000 sec. The stability and specific surface area of the material decreased, but the catalytic activity of oxygen reduction was improved by.TEM, HRTEM, XPS and XRD. It is shown that the optimum pyrolysis temperature is 800 C, and the obtained material (Co POP-800) has the highest catalytic activity. Its catalytic performance is similar to that of commercial Pt/C, and even better. In addition, the oxygen reduction of Co POP-800/C is reduced to 4 electron catalytic mechanism, the oxygen is reduced to water directly, and Co POP-800/C also has excellent methanol tolerance and stability. Qualitative.3. obtained a Fe-Nx/C catalyst by pyrolysis of a new porous, high specific surface area iron porphyrin based polymer, and applied it to the air cathode of a single chamber microbial fuel cell. In neutral medium, Fe-Nx/C showed good catalytic performance in oxygen reduction. This may be due to the carbon layer of iron based nanoparticles and nitrogen doped graphite. Synergistic catalysis is produced. In addition, microbiological fuel cells of the Fe-Nx/C cathode exhibit better performance than the Pt/C cathode for microbial fuel cells, which are shown in better battery voltage, maximum power density and Kulun efficiency. These studies show that Fe-Nx/C is more adaptable and tolerable to bacteria than Pt/C. The fuel cell system has better practical prospects.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O643.36;TM911.4

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