单个掺杂石墨烯纳米片上缺陷微观结构的设计与电化学研究

Graphene, a one-atom layer of graphite, possesses a unique two-dimensional (2D) structure.Thus, it is expected to be a promising electrode material with high performance for new energy storage and conversion. Both intrinsic defects (vacancies, edges et al.) and extrinsic defects (heteroatom doping ) in graphene sp2 domains are crucial for its eletrochemical properties. So it is the key to design the type and microstructure of defects, and research their relation to the heterogonous ET kinetics dynamics for improving the electrochemical properties of graphene. Early reseach has proved that the intrinsic structural defects affect the heterogonous ET kinetics dynamics at graphene, then the project will continue to reveal how the external defects affect the heterogonous ET kinetics dynamics of heteroatom doped graphene. It will obtain the different sizes of doped graphene（N-CRGO、B-CRGO and S-CRGO）nanosheets by using different chemical reduced graphene oxides (CRGOs) and controlling the size of flakes. Combining XPS, Raman and nanoelectrode techniques, the project will investigate intrinsic electrochemical properties of individual doped graphene nanosheet, and the detailed relationship between the microstructure of external defects and the heterogeneous ET kinetics dynamics. This project will motivate a direction for reasonable design defect to improve the electrochemical performances of graphene, and consequently to meet the targeted requirements of new electrochemical energy devices.

石墨烯因具有独特的二维结构，已成为新型能源设备的高性能电极材料之一。在石墨烯结构中引入内在型（空位、边缘等）和外在型（掺杂）缺陷，均对其电化学性能有重要影响。因此设计石墨烯缺陷的种类和微观结构，并研究两者对石墨烯电荷转移动力学的影响，是提高其电化学性能的关键。本项目前期工作已证明内在型缺陷能够影响石墨烯的电荷转移动力学；拟在此基础上继续研究外在型缺陷对掺杂石墨烯电荷转移动力学的影响：通过化学还原法和尺寸分离得到不同尺寸的掺杂石墨烯（N-CRGO、B-CRGO和S-CRGO）纳米片，然后结合XPS能谱、Raman光谱和纳米电极技术来研究单个掺杂石墨烯纳米片的本征电化学性质，以及外在型缺陷的微观结构和掺杂石墨烯电荷转移动力学的内在联系，有望通过合理设计缺陷来改进石墨烯的电化学性能，从而为满足新型电化学能源设备的应用要求指明方向。

化学还原方法制备的掺杂石墨烯因制备步骤简单和原料价格低廉，已经能够大量生产并应用到各种电化学设备中。石墨烯基电极材料费米能级处的电子态密度会随着缺陷的增加而大幅度提高，这一独特的电子结构如何影响其本征电化学性质是电化学领域研究的热点。项目围绕掺杂石墨烯化学还原的制备方法以及本征电化学的性质展开研究，并对掺杂石墨烯本征电化学的影响因素即费米能级处的电子态密度进行了探讨。实验测量了氧化还原对在掺氮石墨烯纳米电极上的标准电子传递速率常数k0，发现与水合肼还原石墨烯的本征电化学性质相似。随着水合肼还原石墨烯纳米电极尺寸的增加，其电子态密度会随缺陷密度的减少而减小，而根据Marcus-Hush理论其电子传递速率常数会因非绝热程度增加而减小，这便是石墨烯纳米电极电子传递速率出现尺寸效应的原因。本项目通过测量氧化还原对的标准电子传递速率常数k0，来探讨单个掺杂石墨烯纳米片因缺陷引起电子态密度的改变，进而建立了能够研究其它新型单个二维半导体纳米片电子结构的新方法。