碳改性的铁基氧还原催化剂的制备及其性能研究

发布时间：2018-04-08 15:42

本文选题：碳纳米管　切入点：氮掺杂　出处：《新疆大学》2017年硕士论文

【摘要】：质子交换膜燃料电池(PEMFCs)之所以可以成为一种节能环保、高效的能源装置,主要是因其不受卡诺循环限制、转化效率高、操作温度区间大、比功率和比能量高、污染小、噪声小、原料广、用途多、安全可靠等优点,且在电动车、航天、潜艇、等众多领域都具有应用前景。制备出高活性的催化剂对于提升PEMFCs的性能有着非常重要的作用。目前,Pt/C因其较高的活性成为PEMFCs的商用催化剂,但是仍然有很多的问题存在。例如在长时间的运行过程中,Pt催化剂成本较高、碳载体会对催化剂进行腐蚀、Pt原子发生溶解、稳定性差及与燃料产生混合电位发生中毒等现象,造成催化剂的活性大幅度降低,这些因素都会制约PEMFCs的商业化发展。因此,价格低廉、环境友好、具有高电催化活性的氧还原催化剂的研发成为提高PEMFCs性能的关键。本文以简便的方法合成了三种高效的阴极电催化剂,并对其形貌特征和电化学性能进行了相应的测试。主要研究结果如下:(1)以氯化铁为铁源,三聚氰胺为氮源,氧化石墨烯为载体,采用高温煅烧法制得了三明治夹层结构的Fe3C@NGs复合催化剂,XRD、Raman、SEM、TEM等一系列物理测试结果显示:Fe3C纳米原子均匀分散在褶皱的氮掺杂氧化石墨烯(NGs)薄层上。并考察了氧化石墨烯(GO)负载量对制得的催化剂在碱性介质中的氧还原活性(ORR)的影响。实验结果表明:当GO负载量为80 mg时,所制得的催化剂具有最高的氧还原活性,同时表现出较优的抗甲醇性能和较好的循环稳定性,该催化剂优异的性能归因于较高的含氮量,较丰富的Fe-Nx/C-Nx活性位点、较大的比表面积和较丰富的孔结构。(2)以聚乙烯吡咯烷酮(PVP)为分散剂,采用高温煅烧法原位合成了双功能空心链条状的FN-B-800复合材料,并对煅烧温度和前驱体浓度等因素进行了一系列的考察。实验结果表明:氯化铁浓度为4 mmol,煅烧温度为800°C,所制得的复合催化剂表现出更高的ORR活性和吸氧(OER)活性,良好的甲醇容纳性能及优异的循环稳定性。经分析认为,PVP的使用可将Fe3C纳米粒子均匀分布在空心链条状的氮掺杂碳纳米管(n CNTs)当中,从而有效地阻止Fe3C的聚集或堆积,同时有利于保持活性物质较大的比表面积。(3)以葡萄糖为碳源,尿素为氮源,氯化铁为铁源,采用高温煅烧法制得蜂窝状Fe3C@NGC催化剂。经XRD,SEM和TEM表征可知,Fe3C纳米晶体均匀分布在氮掺杂石墨化碳上。利用电化学工作站对所制得的复合材料的电化学性能进行了测试,通过与Fe3C@GC和NGC相比较,发现Fe3C@NGC催化剂表现出更优的电催化活性、良好的循环稳定性及较优的甲醇容纳性。Fe3C@NGC催化剂所表现出的良好性能主要是由于复合材料提供更大的比表面积、更多的反应活性位点和更通畅的离子传输通道。
[Abstract]:The proton exchange membrane fuel cell (PEMFCs) can be a kind of energy saving, environmental protection and high efficiency energy device, mainly because it is not restricted by the Carnot cycle, has high conversion efficiency, has a large operating temperature range, has high specific power and specific energy, has less pollution, and has less noise.It has many advantages, such as wide raw materials, many uses, safety and reliability, and has the prospect of application in many fields such as electric vehicle, aerospace, submarine and so on.The preparation of highly active catalysts plays an important role in improving the performance of PEMFCs.At present, Pt- / C has become a commercial catalyst for PEMFCs because of its high activity, but there are still many problems.For example, the cost of Pt catalyst is high during a long period of operation, the carbon carrier will corrode the Pt atom, the stability will be poor and the mixed potential with fuel will be poisoned, the activity of the catalyst will be greatly reduced.These factors will restrict the commercial development of PEMFCs.Therefore, the research and development of oxygen reduction catalyst with low cost, environment friendly and high electrocatalytic activity has become the key to improve the performance of PEMFCs.In this paper, three kinds of high efficient cathodic electrocatalysts were synthesized by a simple method, and their morphologies and electrochemical properties were tested.The main results are as follows: (1) using ferric chloride as Tie Yuan, melamine as nitrogen source and graphene oxide as carrier,A series of physical measurements such as Fe3C@NGs composite catalyst with sandwich sandwich structure (Fe3C@NGs) and SEMT-TEM show that the nano-atoms of Fe3C are uniformly dispersed on the thin layer of ruffled nitrogen-doped graphene oxide (NGS).The effect of the loading amount of graphene oxide on the oxygen reduction activity of the prepared catalyst in alkaline medium was also investigated.The experimental results showed that the catalyst with 80 mg go loading had the highest oxygen reduction activity, and showed better methanol resistance and cycle stability. The excellent performance of the catalyst was attributed to the higher nitrogen content.Bifunctional hollow chain FN-B-800 composites were synthesized by high temperature calcination with polyvinylpyrrolidone (PVP) as dispersant, with rich specific surface area and rich pore structure.A series of factors such as calcination temperature and precursor concentration were investigated.The experimental results show that the composite catalyst has higher ORR activity and higher oxygen absorbent activity, better methanol holding capacity and better cycling stability than the composite catalyst with 4 mmol / L ferric chloride concentration and 800 掳C calcination temperature.It is considered that the Fe3C nanoparticles can be uniformly distributed in the hollow chain-like nitrogen-doped carbon nanotubes (CNTs), thus effectively preventing the aggregation or accumulation of Fe3C.At the same time, the honeycomb Fe3C@NGC catalyst was prepared by high temperature calcination with glucose as carbon source, urea as nitrogen source and ferric chloride as Tie Yuan.The results of SEM and TEM show that Fe _ 3C nanocrystals are uniformly distributed on nitrogen-doped graphitized carbon.The electrochemical properties of the composites were tested by electrochemical workstation. Compared with Fe3C@GC and NGC, the electrocatalytic activity of Fe3C@NGC catalyst was found to be better.The good cycling stability and the excellent methanol accommodability. Fe3C@ NGC catalyst showed good performance mainly because the composite provided larger specific surface area more reactive sites and more unobstructed ion transport channels.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TM911.4

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