CO/Mg燃烧合成氮掺杂少层石墨烯及其量子电容效应研究

Supercapacitor with high energy density as well as high power density has attracted increasing attention. Graphene has become a research hotspot as supercapacitor electrode materials recently, due to its extraordinary electric property and chemical stability. High-quality graphene with outstanding capacitive performances has been synthesized through combustion synthesis method, which has the advantages of high reaction temperature, high product crystallinity, ultrashort reaction time and accessibility for large-scale production. This proposed project will explore a novel method for synthesis of graphene by combustion reaction between CO and magnesium. Initial work will focus on reaction kinetics of CO reduction by Mg, then further investigate the control of magnesium combustion process in CO. Nano / micro crystal particles acting as template will be applied to induce assembling of carbon atoms, and micromorphology, species and dosage of the template will be adjusted to realize effective control on the porosity as well as electrochemical properties of graphene. Key factors and rules influencing the reduction morphology of carbon and structure properties of grapheme will be explored. Nitrogen doped few-layer graphene will be prepared via direct synthesis strategy. Taking advantage of extremely high temperature conditions produced by combustion reaction and applying catalytic dehydrogenation technology, nitrogenous heterocyclic organic compounds will be carbonized directly, with retained fundamental heterocyclic structures, then co-assemble with carbon atoms converted by CO to form graphene. The method and mechanism, through which the doped nitrogen atom configuration in graphene can be controlled accurately, will be investigated. The mechanism and law of different nitrogen dopant configuration/concentration effecting on capacitance performances of graphene will be clarified. Additionally, the relationships between Nitrogen doping characteristics, quantum capacitance effect and capacitive properties, such as rate capability and cycle life, will also be revealed. This project will provide experimental/theoretical basis for constructing supercapacitor system with high energy density as well as ultrahigh power density.

“双高”型超级电容器日益受到关注，石墨烯近年来成为超级电容器材料研究的热点。燃烧合成法反应温度高、产物结晶度、耗时极短、易于规模化，能够制备出电容性能优异的高品质石墨烯。本项目将探索CO/Mg燃烧合成少层石墨烯的新技术，首先研究CO/Mg燃烧反应的动力学和过程控制，利用纳微晶体为模板诱导碳原子组装，调节模板的种类和用量，实现对石墨烯孔结构与性能的调控，探索影响碳沉积形态和石墨烯结构性能的因素与规律；在此基础上，采用直接合成方式进行氮掺杂，利用催化脱氢技术及燃烧反应产生的极高温条件，使含氮杂环有机物直接炭化并保留环状基本结构，与CO转化碳原子共同组装成石墨烯，研究掺杂氮原子构型的精准调控机制与方法；进而研究不同构型氮杂原子对石墨烯电容性能的影响机理与规律，揭示氮掺杂特性、量子电容效应与石墨烯倍率性能、循环寿命等电容性能的关系，为构建高比能量、超高比功率超级电容器体系提供实验依据和理论基础。

“双高”型超级电容器日益受到关注，石墨烯近年来成为超级电容器材料研究的热点。氮掺杂是改善石墨烯电容性能的重要手段。.本项目首次探索了CO/Mg燃烧反应合成少层石墨烯的新技术，系统研究了反应工艺参数与材料理化性能之间的关系。通过调节模板的种类和用量等条件，实现了对石墨烯孔结构与性能的调控，比容量最高可达179.4F/g。在此基础上，以多种固态环化有机物作为氮源，通过CO/Mg的自蔓延燃烧反应将氮原子原位掺入石墨烯中，研究了不同氮源种类、氮源用量等工艺参数对于氮掺杂石墨烯结构的影响。固态氮源中的氮含量及其用量对石墨烯产物的比表面积有较大影响，掺氮后石墨烯的比表面积大幅下降。以六次甲基四胺为氮源的掺杂石墨烯，氮原子表现为混合结构形式存在，其中吡啶氮结构的比例最高超过70%，在功率密度35kW/kg时能量密度仍保持38.88Wh/kg。.深入研究了单一构型氮掺杂石墨烯的制备方法及掺杂氮构型与含量调控方法，分析了影响氮掺杂不同构型形成的原因。采用三聚氰胺和聚(4-乙烯吡啶)作为氮源，成功制备了单一吡咯型和单一吡啶型氮掺杂石墨烯。使用混合氮源，实现了石墨烯中吡咯型和吡啶型掺杂氮的有效调控，并揭示了吡啶氮构型的形成优先于吡咯构型的规律。通过模拟自蔓延燃烧反应瞬间形成高温环境的加热方式，发现瞬时高温可以使氮源转化为均质产物的现象，阐明了石墨烯中单一构型掺杂氮形成的机制。.研究了不同构型氮杂原子对石墨烯电容性能的影响机理与规律。吡咯型和吡啶型氮掺杂石墨烯均表现出优异的倍率性能，吡啶型氮更利于石墨烯倍率性能的提升。含氮量为5.2 at%的单一吡啶型氮掺杂石墨烯面积比容量则高达43.07 μF/cm2，较单层石墨烯的理论面积比容量提高了115.35%。理论计算表明，氮掺杂可以显著提高石墨烯的量子电容，对于单层石墨烯，吡啶氮掺杂对量子电容的影响更大；而对于多层石墨烯，吡咯氮掺杂对提高量子电容更有利。本项目研究结果可为构建高比能量、超高比功率超级电容器体系提供实验依据和理论基础。