基于生物质的垂直石墨烯制备及其缺陷在氧还原反应中的电化学催化机理研究

The limited source and high cost of Pt have made the Pt-based catalysts the primary barrier for commercial applications of fuel cells. Defective nanocarbons that have demonstrated excellent catalytic ability are alternative catalysts stead of Pt in ORR. It is critical to reveal the electrocatalytic mechanism of defects in ORR for designing the highly effective catalyst. In this project, vertical graphene obtained from biomass by microwave plasma irradiation with the optimized conditions including plasma power and irradiation time will be studied, modified or doped by radio frequency plasma for controlling the defect type and quantity, and its defects and their synergistic effects with other elements on the electrocatalytic performances of ORR will be investigated systemically. After characterizing the structure and type of defects, we will study construction process of catalytic sites between the defects and other elements, verify the structure, type and composition of catalytic sites, and analyze the oxygen reaction path and electrocatalytic mechanism of catalytic sites in ORR. Combined with experimental results, density functional theory will be employed to simulate the catalyst mechanism of ORR, and attempts to reveal the essence of synergic catalysts and their mechanism in ORR. This project will provide the technical and theoretical basis for synthesizing novel carbon-based free-metal ORR catalysts.

铂的储量少、成本高成为燃料电池普及应用中的主要障碍，含有缺陷的纳米碳材料所显示的优异催化性能使之可能成为铂在快速氧还原中的替代物，而揭示缺陷在氧还原反应中的活性机理是设计出高效催化剂的关键。本项目以利用微波等离子体轰击生物质原料并通过优化实验工艺包括等离子体功率及轰击时间制备的垂直石墨烯作为基础材料，采用射频等离子体技术对缺陷的种类和数量进行调控，并系统研究缺陷及与其他元素协同效应对氧还原反应催化性能的影响。通过表征缺陷结构及类型，研究缺陷与其他元素活性中心的构建过程，明确催化活性位点的结构、种类和成分，探究各活性位点氧还原反应的路径和催化机制。采用密度泛函理论进行氧还原催化机制的模拟研究，结合实验数据，揭示缺陷与其他元素对氧还原反应协同催化的本质和原理。本项目的实施将为制备新型碳基无金属氧还原反应催化剂的提供技术基础和科学依据。

采用非金属碳材料代替铂等贵金属作为燃料电池阴极氧还原反应催化剂是近年的研究热点。本项目采用微波等离子体轰击技术，选取纤维素、竹子等生物质材料为原料制备垂直石墨烯（VG）薄膜，利用其高导电性、多离子扩散通道、丰富的缺陷等特点，用于氧还原反应（ORR）催化性能的研究。本项目从VG薄膜合成、结构调控及其ORR电催化性能优化等方面开展工作，重点研究微波等离子体轰击合成VG的生长规律，揭示生物质原料转变成纳米碳材料的机理；利用Ar、O2、N2等气体的等离子体对VG薄膜表面结构进行修饰改性，调控缺陷种类，包括边缘缺陷、空位缺陷及杂原子掺杂缺陷等，通过拉曼光谱、X射线光电子能谱、高分辨率透射电子显微镜等表征手段确定缺陷的种类，全面系统地研究VG缺陷结构与ORR催化性能关系，包括各活性位点及协同效应对ORR的催化原理、氧还原能力及反应路径、耐甲醇干扰、抗CO中毒等的依存关系。通过理论计算模拟，结合实验数据对VG的ORR催化机制进行深入探讨，为开发新型的燃料电池阴极ORR催化材料提供理论依据。