可控生长石墨烯的理论研究

Graphene is one of hot and cutting-edge topics for research and application in nanoscience and nanotechnology. Currently, Controllable synthesis of graphene with homogenous properties and controllable structures (sizes, edges and layers) is still a big challenge, and a key issue in the development of graphene. In response to these issues, the overall aim of this project is to systematically investigate controllable synthesis of high-quality and uniform graphene at atomic/molecular level by using density functional theory calculations. We aim to: (1) simulate the graphene growth of different edges without any catalysts under different synthesis conditions, which should reveal preferential growth mechanism for a series of different graphene edges by exploring different reaction paths as well as their precise potential energy surface, activation energy barrier, and so on; (2) simulate various graphene edges growth on different catalytic surfaces including SiC semiconductor, metal, metal alloy, and metal carbide, which should reveal the different growth mechanisms in different processes of "horizontal growth", "vertical growth", "surface catalytic self-limiting growth" and "C segregation/precipitation layer-by-layer growth", as well as finally reveal regulatory mechanism of catalytic surfaces in control growth of high-quality and uniform graphene; (3) investigate the induced mechanism of optical, electrical, and magnetic fields in the control growth of high quality graphene. Ultimately, a rational solution will be put forward for the control synthesis and applications of high-quality and uniform graphenes.

石墨烯是纳米科技研究领域的热门前沿课题之一。石墨烯性质和结构(形状、尺寸、边缘态和层数)的可控制备是石墨烯材料发展中的一大挑战，是困扰石墨烯实际应用的核心问题之一。基于上述问题，本项目采用密度泛函理论计算，从原子/分子层面上系统研究：1）石墨烯不同边缘态在不同合成条件下的本质生长机理。确立石墨烯不同边缘态外延生长的反应路径及其势能面、活化能，揭示石墨烯特定结构边缘态可控生长的调控机制；2）模拟计算不同石墨烯片层在不同类型催化剂（SiC、金属、金属合金和金属碳化物）表面上沉积、成核和生长的过程。揭示石墨烯"平躺式"、"站立式"、"表面催化自限制式"和"表面偏析层-层式"等生长模式的生长机理及其差异。揭示不同催化剂在石墨烯不同生长模式中的不同催化机理及催化剂对石墨烯可控生长的调控机制；3）研究光、电、磁等外场对可控生长高质量石墨烯的诱导机制。为石墨烯的有效可控制备生长和应用提供合理的解决方案。

可控制备结构(形状、尺寸、边缘态和层数)和性质均一的石墨烯是石墨烯材料发展中的一大挑战，是困扰石墨烯材料实际应用的核心问题之一。基于上述问题，本项目采用密度泛函理论计算，从原子/分子层面上系统研究了：（1)石墨烯不同边缘态微观几何结构、物理化学特性, 揭示了不同边缘态微观几何结构、物理化学特性的本质差异和由此所直接导致反应活性和催化活性的差异, 揭示了不同条件下石墨烯特定结构边缘态可控生长的本质机理；（2）一系列不同厚度（单、双和三层）石墨烯与SiC衬底不同晶面（硅面和碳面）、中间体Si、C原子、TiC插层及其缓冲层的界面相互作用及其界面性质；揭示了由于SiC衬底不同终止晶面（硅面和碳面）的化学活性的差异而导致的不同生长机理；揭示了中间体Si、C原子、TiC插层及其缓冲层对SiC热解析可控生长石墨烯的诱导机理和调控机制；（3）一系列不同厚度石墨烯片层与Cu,Ni两类代表性金属及其二元合金（Cu/Ni）和引入六方硼氮H-BN插层的界面相互作用及其界面性质；揭示了通过有效调控二元合金之间掺杂量、掺杂位置以及引入h-BN插层等手段方式，可有效的调控石墨烯与合金催化剂衬底相互作用的强弱和催化活性，从而实现石墨烯层数、均一性的有效可控制备。揭示了不同金属表面、二元合金、以及H-BN插层对石墨烯可控生长的催化机理及其调控机制；（4）一系列不同大小尺寸的Core-shell结构的Fe@Ni、Cu@Ni和Fe@Cu二元金属合金的形成能、结构稳定性、化学活性和催化选择性。此项目的研究为碳化硅、金属和二元合金催化剂的探索设计以及石墨烯的沉积、成核、可控制备生长和应用提供了合理的理论依据和支撑。