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Title:
氮掺杂介孔碳及其负载钴-氧化钴纳米复合材料的制备、表征及电催化性能研究
Author: 刘真真
Degree Level: 硕士
Issued Date: 2016-05
Degree Grantor: 中国科学院大学
Place of Degree Grantor: 北京
Supervisor: 江河清 ; 梁方义
Keyword: 电催化 ; 氮掺杂 ; 介孔碳 ; 钴-氧化钴 ; 氧气还原反应
Subject: 材料
Major: 材料工程
Abstract: 燃料电池被认为是二十一世纪最具潜力的能源动力系统之一,其较慢的阴极氧气还原反应以及较高的过电势是影响燃料电池能量转换效率的主要因素之一。目前,阴极氧气还原反应的电催化剂主要采用贵金属,而贵金属资源稀缺,价格昂贵,这促使人们将研究兴趣逐渐转向资源丰富的过渡金属及其氧化物。将过渡金属及其氧化物与具有优异电子传输性能的多孔碳材料相结合,所获得的纳米复合催化剂可以加快氧气还原反应的动力学,因此越来越受到广大科研工作者的重视。本论文采用一锅法制备了氮掺杂介孔碳及其负载钴-氧化钴纳米复合材料,对其微观形貌、物理和化学性质进行了表征和分析,并深入研究了其电催化氧还原的性能。 首先,以3-氨基酚为碳源和氮源,选取三嵌段共聚物F127为模板剂,在水溶液中,六亚甲基四胺缓慢分解,释放出的甲醛与3-氨基酚在氨水的催化作用下发生聚合反应生成氨基化聚合物,经过高温处理可以得到氮掺杂的介孔碳(Nitrogen-doped Mesoporous Carbon, NMC)。其中,在600 °C煅烧所获得介孔碳中氮含量为 9.1 wt %,比表面积为410.8 m2 g-1,孔体积为0.297 cm3 g-1。该材料催化的电化学反应中二电子氧还原反应占主导地位,在O2饱和的浓度为0.1 mol L-1 的KOH水溶液中,扫描速率为10 mV s-1、转速为1600 rpm的条件下,该电化学氧气还原催化反应的起始电位为 -0.25 V。 其次,在上述一锅法反应体系中,同时加入六水硝酸钴,待聚合反应完成后进行高温煅烧,从而获得氮掺杂介孔碳负载钴-氧化钴纳米复合材料(Co-CoOx/NMC)。在600 °C煅烧所获得复合材料仍然呈现介孔结构,其比表面积为423.7 m2 g-1,孔体积为0.314 cm3 g-1。该复合材料中钴主要以Co0、Co2+和Co3+三种形式存在,Co-CoOx颗粒均匀地分散在介孔碳骨架上,其粒径为6-20 nm。该材料催化的电化学反应中四电子氧还原反应占主导地位,随着钴掺杂量的增大,其对电化学氧气还原反应的催化性能逐渐增强。在O2饱和的0.1 mol L-1 KOH水溶液中,扫描速率为10 mV s-1、转速为1600 rpm的条件下,电化学氧气还原催化反应的起始电位为 -0.11 V。 在本论文中,以3-氨基酚为前驱体,所形成聚合物中的氨基可作为锚点,与钴前驱体发生相互作用,实现复合材料中钴-氧化钴颗粒的均匀分散。研究表明在氮掺杂的介孔碳体系中引入钴,可以显著提高其电催化氧还原反应的性能,不仅电流密度明显增大,同时过电位显著降低。
English Abstract: Fuel cells are considered as one of the most promising energy and power systems of the 21st century. However, the slow reaction rate and high overpotential of the oxygen reduction reaction on cathode are the main factors to impede the energy conversion efficiency in fuel cells. Presently, the platinum group metals are the most popular catalysts for oxygen reduction reaction, but the resources are very scarce and expensive. Thus, researchers have adjust their interests to the abundant transition metal resources. Nanocomposite catalysts could be obtained by combining the transition metal/metal oxides with porous carbon materials which have excellent electron transport properties, and they have drawn a lot of attention because they can accelerate the oxygen reduction reaction dramatically. In this thesis, we have prepared nitrogen-doped mesoporous carbon and the related nanocomposites containing cobalt-cobalt oxides particles through one-pot method, followed by characterization and analysis of their morphology, physical and chemical properties. Then, their electrocatalytic performances for oxygen reduction reaction have been studied. Firstly, in aqueous solution, with 3-aminophenol as carbon and nitrogen sources, we chose the triblock copolymer F127 as a template, formaldehyde slowly generated from the decomposition of hexamethylenetetramine, reacted with 3-aminophenol to form aminated polymer under the catalyst of ammonia. Nitrogen-doped mesoporous carbon (NMC) was obtained after the calcination of the aminated polymer. After treating at 600 °C, the material containing 9.1 wt % nitrogen content, exhibits a specific surface area of 410.8 m2 g-1, a total pore volume of 0.297 cm3 g-1. This material tended to catalyze the oxygen reduction reaction mainly in a two-electron reaction pathway, and the onset potential was about -0.25 V in oxygen-saturated 0.1 M KOH with a scan rate of 10 mV s-1 and a rotational speed of 1600 rpm. Secondly, Co(NO3)2·6H2O was introduced to the above one-pot reaction system. The nitrogen-doped mesoporous carbon supported cobalt-cobalt oxide nanocomposites (Co-CoOx/NMC) was obtained after calcination. It was found that the mesoporous structure was maintained. The sample calcinated at 600 °C showed a specific surface area of 423.7 m2 g-1 and a total pore volume of 0.314 cm3 g-1. In the composite system, cobalt presented in the forms of Co0、Co2+ and Co3+, and the cobalt-based particles (Co-CoOx) with the size of 6-20 nm, were well distributed in the nitrogen-doped mesoporous carbon matrix. This material tended to catalyze the oxygen reduction reaction mainly in a four-electron reaction pathway, and performed much better with the increasing amount of the cobalt into the reaction system. The onset potential was around -0.11 V in oxygen-saturated 0.1 M KOH with a scan rate of 10 mV s-1 and a rotational speed of 1600 rpm. In this thesis, using 3-aminophenol as the precursor, the amino groups in the obtained polymers could interacts with the cobalt precursor, resulting in the uniform dispersion of the cobalt-cobalt oxide particles in the composites. The study showed that the introduction of cobalt species into the nitrogen-doped mesoporous carbon matrix could dramatically improve the electrocatalytic performances of oxygen reduction reaction, with increased current density and decreased overpotential.
Language: 中文
Department: 膜分离与催化团队
Available Date: 2020-07-01
DOC Type: 学位论文
Content Type: 学位论文
URI: http://ir.qibebt.ac.cn/handle/337004/9779
Appears in Collections:膜分离与催化团队_学位论文

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Recommended Citation:
刘真真. 氮掺杂介孔碳及其负载钴-氧化钴纳米复合材料的制备、表征及电催化性能研究[D]. 北京. 中国科学院大学. 2016.
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文件名: 氮掺杂介孔碳及其负载钴-氧化钴纳米复合材料的制备、表征及电催化性能研究.pdf
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