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石墨相氮化碳(g-C_3N_4)由于不含金属组分、化学性质稳定、且具有可见光响应,在光催化领域具有越来越广阔的应用前景。本文基于密度泛函理论的平面波超软赝势方法,对不同原子层数的g-C_3N_4的表面能、电子结构和光学性质等进行了研究。结果表明:g-C_3N_4的表面能随着原子层数的增加而逐渐降低,从6层原子开始表面能小于0,说明当原子层数大于6时,g-C_3N_4形成稳定的层状表面结构;不同层数的g-C_3N_4表面结构均为间接带隙半导体,导带底主要由C的2p态和N的2p态杂化而成,价带顶主要由N的2p态和N的2s态构成。本文研究结果为层状结构的g-C_3N_4催化材料的设计、制备和催化性能研究提供了理论依据和数据基础。
Graphite carbonitride (g-C_3N_4) because of its non-metallic components, chemical stability, and has visible light response, in the photocatalytic field has more and more broad application prospects. In this paper, surface energy, electronic structure and optical properties of g-C_3N_4 with different atomic layers are studied based on density functional theory (PFT) plane wave ultra-soft pseudopotential method. The results show that the surface energy of g-C_3N_4 gradually decreases with the increase of the number of atomic layers. The surface energy of g-C_3N_4 decreases from 0 to 6, indicating that g-C_3N_4 forms a stable layered surface structure when the number of atoms is more than 6. The surface layers of g-C_3N_4 with different layers are all indirect band gap semiconductors. The bottom of the conduction band is mainly composed of the 2p state of C and the 2p state of N, and the top of the valence band is mainly composed of the 2p state of N and the 2s state of N . The results of this paper provide a theoretical basis and a data basis for the design, preparation and catalytic performance of the g-C_3N_4 catalytic material with layered structure.