三维网络结构石墨烯电极表面官能团调控及电容性能研究

The capacitance performace of a supercapacitor is largely determined by the nature of the electrode materials. Designing and development of high-performance electrode with high specific capacitance, more accessed surface area and excellent cyclability remains an interesting topic in electrochemical energy storage. The graphene has been showing promising applications as electrode materials in supercapacitor because of its excellent electronic conductivity, good mechanical property and theoretically high surface area. Moreover, the oxygen/nitrogen-containing surface functional groups on 2D graphene plane could substantially improve its specific capacitance by providing additional pseudocapacitance with electrolyte. However, the inherent properties like easy aggregation during process, low specific capacitance and slow diffusion dynamics of electrolyte within graphene electrode, greatly restrict their wide applications in supercapacitor industry. In this project, a series of 3D graphene architecture with interconnected network for rapid ion transport will be developed based on the electrochemical deposition, electrostatic assembly and template-directed synthetic methods. 3D porous substrates like sponge, nickle foam will be adoped as scaffolds to grow graphene nanostructure with controlled macroscopic morphologies and tunable sheet thickness, while the surface functional groups on graphene plane will be controlled by selecting different reduction pathways, like in-situ UV reduction, thermal reduction in different atmospheres, and chemical reduction with various reduction reagents. By measuring the electronic conductivities of graphene electrodes and systematically investigating their capacitance performances in both aqueous and nonaqueous electrolytes, the correlation between the functional groups (the number and sort), the electronic conductivity, the capacitance behavior (specific capacitance, charge/discharge rate, charge storage mechanism and cycle performance) and the 3D graphene network will be demonstrated. As a result, the synthetic methodology used for preparing high-performance graphene electrode with maximum exposed electrochemically active surface area will be developed. In addition, the supercapacitor with high energy, high power density and excellent cycle performance will also be configurated through optimizing the structure of graphene electrode and selecting appropriate electrolyte. It is anticipate that our findings would provide useful experiment data for graphene-based materials that may find promising applications in micro-electronics, photovoltaic cell, catalysis and biotechnology.

电极材料的微观结构决定超级电容器的主要性能，设计高比电容和高循环稳定性的电极材料已成为当前储能器件的研究热点。针对目前石墨烯电极普遍存在易团聚、比电容低、离子迁移路径长等问题，基于石墨烯三维网状结构兼具防团聚、快速离子迁移及高表面积的优点，本项目以氧化石墨烯和低碳氢化合物为前驱体，利用化学气相/电化学沉积及无机模板导向合成等技术，制备系列三维网络结构石墨烯电极；通过选择不同的还原方法及控制还原参数，调控石墨烯网络骨架表面含O/N官能团的种类和数量；研究不同电解质在石墨烯三维网络结构内的扩散动力学，揭示含O/N官能团在不同电解质中的储能机理、电荷转移速率、循环寿命等电化学规律；建立不同电解质中石墨烯三维网络结构、官能团种类、数量等与其导电性和电容性能的内在联系；发展官能团特征和三维网络结构可控的石墨烯材料制备新方法，为构建高性能石墨烯基超级电容器提供实验依据和技术支持。

本项目以氧化石墨烯和二茂铁、苯乙烯等为前驱体，以MgO、MgAl-LDO、泡沫镍等为无机模板，利用化学气相/电化学沉积等技术，制备了石墨烯纳米筛、超薄碳纳米筛、三维网络结构石墨烯等电极；通过H3PO4活化石墨烯气溶胶，在构成气溶胶的石墨烯片层上创制纳米孔；利用赝电容修饰石墨烯纳米筛，获得了兼具高容量和高倍率性能的复合电极；基于EDTA-3K与石墨烯氧化物自组装及化学活化技术，获得了碳层包覆高表面石墨烯电极材料；系统地研究了上述电极材料在水系电解质（6.0 M KOH），有机电解质（TEABF4/AN）中的循环伏安、充放电性能以及离子扩散动力学性能；发现以石墨烯纳米筛为基本单元构成的三维网络结构电极材料，能显著提高电极的利用效率，增加孔洞边缘含氧官能团参与赝电容的几率，提升电极的比电容、倍率性能和循环稳定性。此外，本项目还将制备石墨烯纳米筛的化学活化方法应用到活化纤维素类材料，获得了具有快速电子/离子传输特性的柔韧织构碳布，组装了基于全固态柔性电容器器件，系统研究了器件的充放电性能、稳定性以及能量-功率特性曲线。. 上述结果在Energy Environ. Sci、 Adv Funct Mater、Nano Energy、Nanoscale、CARBON、J Phys Chem C等上发表论文14篇，包括邀请综述一篇（Energy Environ. Sci, 2016, 9, 1891）和前封面论文一篇（Adv Funct Mater, 2015, 25, 5420）。发表的研究论文中，2篇入选ESI高被引论文（Energy Environ. Sci, 2016, 9, 1891; Carbon, 2015, 93, 315），2篇论文曾入选ESI热点论文（Carbon, 2015, 93, 315；Carbon, 2015, 92, 1）。培养博士研究生1名，硕士研究生16名，其中已经毕业研究生9名，3人获得研究生国家奖学金，1人获得中国化学会第30届学术年会优秀墙报奖，2人获陕西师范大学优秀学位论文。参加国际电化学储能会议2人次，国内电化学储能相关会议10余次，受邀口头报告6次。研究成果“高能量密度超级电容器电极材料的设计、组装及应用基础研究”获陕西省高等学校科学技术一等奖（第二完成人）。