三维开放孔结构碳纳米管/石墨烯复合材料与电极的构筑及其基础问题研究

The usage of the Pt catalyst poses a great challenge to the development of fuel cell technology; therefore, it is urgent to explore novel non-noble metal based electrocatalysts. Nanostructured nitrogen-doped carbon features high electronic conductivity and specific surface area, which are highly desired to be used as the electrocatalyst in fuel cells. This proposal is aimed to develop the nitrogen-doped openly 3-D porous carbon nanotube-graphene composite material, in which the carbon nanotube functions as the stereo-support to avoid the self-segregation of graphene sheets. On one hand, the high specific surface area of the graphene can be maintained in this composite structure, which facilitates the dense assembly of the active sites. On the other hand, the openly 3-D porous structure facilitates the mass transfer of the active species into the electrode, which makes the high-efficiency utilization of the active sites. Accordingly, the polarization loss of kinetics and mass transfer can be effectively decreased in fuel cells. In this project, carbon nanotube is directly grown on the surface of the graphene by using linear polymer-based precursors like polyaniline. Then, the surface analysis is used to generate a chemical model to describe the surface composition/structure. The result is then correlated with the electrocatalytic activity to clarify the role of the transition metal and the dopant nitrogen, and finally the intrinsic nature of the active sites. Also, the optimization on the openly porous structure ensures the fast mass transfer and thus the high-efficiency utilization of the active sites, and thereby ensures a high output power density of the fuel cells. Basically, this research work presents the results on the synthesis chemistry and intrinsic nature of the nitrogen-doped carbon in a fundamental way, as well as an interesting openly porous nanostructure from the engineering point of view. Therefore, this research project will definitely shed light on the rational design and development of the non-noble metal electrocatalyst for fuel cells.

掺杂型纳米结构碳因具良好的导电性和高比表面积，是一类备受关注的氧还原反应电催化材料。本项目拟探索基于一维碳纳米管和二维石墨烯的三维开放孔结构材料，利用碳纳米管支撑功能减少石墨烯团聚，实现材料表面活性位点的密集组装，促进物料在开放孔道内的传输，降低电极内反应动力学与传质极化损失。本项目以线性高分子（如聚苯胺）为碳源在石墨烯基底上原位生长碳纳米管，开展相关制备科学研究，获得组成/结构可控的氮掺杂碳纳米管/石墨烯复合材料；基于表面分析结果构建电催化活性中心的化学模型，从原子/分子层面阐明材料“构-效”关系；通过调控材料比表面积与孔结构特征，提高活性位点在电极内的密集组装与高效利用，提高燃料电池性能。本项目的研究将丰富新型纳米结构氮掺杂碳材料选控制备科学内容，深化表面电催化反应及电极荷质耦合传递过程认知，为探索新型催化剂体系和电极结构提供理论指导和开发思路，具有重要的理论意义和应用价值。

用低廉的、高活性的材料替代贵金属电催化剂是发展燃料电池的关键。掺杂型纳米结构碳因具良好的导电性和高比表面积，是一类备受关注的氧还原反应电催化材料。本项目采用纳米浇筑法制备氮掺杂介孔碳材料，通过引入不同的共模板、调变共模板的浓度、改变表面活性剂的类型等，制备了一系列氮掺杂介孔碳材料，并结合相关物化表征和电化学分析方法，研究了催化剂材料的组成、结构、维度等对氧还原活性的影响。利用氧化石墨烯和聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物(P123)作为双模板合成一种新颖超薄二维二氧化硅膜，其具有高比表面积和指纹状平行介孔的结构特征，基于此材料制备所提出的协同组装机理可为介孔材料的形貌调控提供指导。引入氧化石墨烯共模板合成超薄（1 nm）的二维氮掺杂分级介孔碳(2DNHPC)，发现2DNHPC具有极高的纵横比（几百）和大孔与介孔的分级多孔结构，这些独特的结构特征促进传质和活性位的利用，进而提高氧还原的性能。以三嵌段共聚物F127为表面活性剂、调变氧化石墨烯共模板的浓度，进一步调控二维二氧化硅膜的纹理特征，再以其为硬模板合成相应的具有介孔结构、高比表面积、二维形貌的碳材料在碱性介质中氧还原性能均优于铂。.从催化剂的载体效应（尺寸效应）以及合金效应的影响出发，进行了Pt基催化剂的载体研究，采用二维氮掺杂有序介孔碳（NOMC-2D）、三维氮掺杂有序介孔碳（NOMC-3D）分别作为Pt基催化剂的载体，探究载体维度对Pt基催化剂甲醇氧化活性及抗毒化性能的影响，结果表明，所制备的Pt/NOMC-2D催化剂比Pt/NOMC-3D和商业Pt/C催化剂表现出更高的甲醇氧化活性与抗毒化作用。采用过渡金属Ni为核，通过化学置换法外延生长Pt壳层，所制备的PtNi2/XC-72氧还原反应活性优于商品Pt/C催化剂。.通过高温熔盐法合成了硫掺杂碳材料，熔融的K2S作为高浓度硫源的同时也提供了盐浴，这样形成的固液两相界面，促进了硫源和碳源的接触，有利于硫的掺杂，制备的硫掺杂碳材料含硫量最高达到了1.50 at.%（原子比），用S原子去掺杂碳材料，可以有效提高其氧还原的性能。项目的完成对燃料电池的发展有重要的促进作用。