核壳结构Co@PtM/石墨烯纳米复合材料的构筑及其电催化性能

Research and development of core-shell structured electrocatalysts can greatly reduce the usage of Pt and increase the utilization efficiency of noble metal electrocatalysts, which is an important way to solve the bottleneck problem of the large-scale commercialization of fuel cells. In this item, core-shell structured Co@PtM (M=Ru, Pd, Rh) electrocatalysts with low Pt loading are prepared by using graphene as the support, which has ordered two-dimensional plane structure, high specific surface area, and high conductivity. In addition, cobalt is chosen as the core because of its relatively low price. The growth mechanism of Co/graphene composites and the shell are described through the effects of process conditions on the particle size, crystallinity and morphology of Co nano-particles, as well as the growth of shell. The influence of shell composition, mole ratio of core to shell,particle sizes of Co core on the electrocatalytic performance of Co@PtM/graphene（M=Ru,Rh,Pd）are further invesigited.The interface effect of Co@PtM/graphene, forming mechanism of the core-shell structure and the interaction mechanism between core and shell are revealed. Finally,the electrocatalytic performance of core-shell structured composites for small organic molecules (methanol, ethanol and formic acid) oxidation and structure-activity relationship are explored. The results of this project will provide theoretical basis for the design and preparation of core-shell structured catalysts and have important significance on the development and application research of core-shell structured electrocatalysts, as well as the forming mechanism of core-shell structure and the interaction mechanism between the core and the shell.

研制和开发核壳结构催化剂可大幅度降低Pt使用量、提高贵金属催化剂利用率，是解决燃料电池大规模商业化瓶颈问题的重要途径。本项目拟利用具有规整二维平面结构、大比表面积和高导电性的石墨烯做载体，以价格相对低廉的钴为核，研制低铂壳层核壳结构Co@PtM/石墨烯（M=Ru,Rh,Pd）电催化剂，通过工艺条件对钴纳米颗粒尺寸、结晶度和形貌、壳层生长过程及壳的组成、核壳摩尔比、Co核尺寸大小对催化剂的电催化性能的影响研究，阐述Co/石墨烯复合材料及壳层生长机制，揭示Co@PtM/石墨烯复合材料的界面效应、核壳结构形成机理及核壳相互作用机理，探索Co@PtM/石墨烯（M=Ru,Rh,Pd）复合材料对有机小分子（甲醇、乙醇和甲酸）氧化的电催化性能及构效关系。本项目研究将为核壳结构催化剂的制备提供理论基础，对于核壳结构电催化剂的发展、应用研究及认识核壳结构形成和核壳相互作用机理有重要意义。

催化剂对于燃料电池非常重要。研究发现Pt由于它特殊的电子结构最适合作为低温燃料电池催化剂的活性组分，但是Pt作为催化剂也存在以下缺点：Pt在世界上的储量较少以及商业价格过高导致催化剂成本较高；Pt易被醇类催化氧化反应过程中产生的CO副产物毒化，极大的降低催化剂活性。另外载体对于催化剂性能的优劣具有重要的影响。石墨烯以其特殊的单层碳原子二维结构的特性，具有较高的电子转移速率和较大的比表面积，适合作为催化剂载体。本项目利用石墨烯做载体，研制核壳结构Co@Pt/石墨烯和低铂基催化剂，通过工艺条件对钴纳米颗粒尺寸、结晶度和形貌、及核壳摩尔比、Co核尺寸大小、CNT添加对催化剂的电催化性能的影响研究，揭示核壳结构形成机理，探索复合材料对有机小分子氧化的电催化性能及构效关系。结果表明，分别以鳞片石墨(LG)、膨胀石墨(PG)和超细石墨粉(SG)为原料时，Pt/Gr催化剂对甲醇氧化的电催化性能和稳定性大小顺序为Pt/SGr>Pt/PGr>Pt/LGr，其性能都高于Pt/C催化剂。Pt/Gr-C催化剂对甲醇氧化的电催化活性达0.3 A/mgPt，分别是Pt/Gr (0.22 A/mgPt) 和Pt/C (0.18 A/mgPt)的1.4倍和1.7倍。粒径约3 nm的核壳结构Co@Pt/Gr对甲醇氧化的峰电流密度为0.22 A/mgPt，是Pt/Gr催化剂对甲醇氧化催化能力的1.6倍。粒径25 nm的核壳结构Co@Pt/Gr对甲醇催化氧化峰电流密度达到1.06 A/mgPt，是Pt/Gr催化剂对甲醇氧化催化能力的5倍，抗中毒能力提高30%。核壳结构Co@Pt/Gr的石墨烯片层中加入CNT，可使石墨烯的缺陷更多，混乱度更强，增大了催化剂的电化学活性表面积，从而可提高催化剂活性。本项目研究将为核壳结构催化剂的制备提供理论基础，对于低铂催化剂的发展、应用研究有重要意义。