咔唑类化合物在MoS_2晶体表面吸附行为的第一性原理

First Principles of the Adsorption of Carbazole Compounds on MoS_2

基于密度泛函理论,采用VASP方法研究了咔唑类化合物(咔唑、3-甲基咔唑和1,5-二甲基咔唑)在MoS2(00-3)晶体表面的吸附行为,考察引起其吸附能差异的原因。结果表明,咔唑类化合物在MoS2晶体表面的吸附过程中为电子受体,其吸附能随MoS_2片层数的增多而减弱;由于空间位阻和电子效应的共同作用,使得咔唑类化合物在MoS2晶体表面的吸附能随着苯环上甲基取代数目的增加而变小;Bader电荷及高低占据轨道的分析表明,咔唑类化合物分子上N原子得电子多少的顺序与它们在MoS2晶体表面的吸附能大小顺序一致,吡咯环N原子上的电子流向催化剂Mo原子,同时咔唑类化合物分子的LUMO轨道接受S原子HOMO轨道的电子形成反馈键,使得咔唑类化合物在MoS2晶体表面稳定吸附。

The adsorption behavior and adsorption energy of three carbazole compounds （carbazole, 3-methylcarbazole, 1,5-dimethylcarbazole） on MoS2 cluster were investigated by the VASP package based on the Density functional theory （DFT）. The results showed that carbazole compounds were electron acceptors in the process of adsorption on the surface of MoS2 and the adsorption energy of carbazole compounds on MoS2 reduced along with growing amount of MoS2 slabs. As the amount of methyl substitution on benzene ring increased, the adsorption energy of carbazole compounds on MoS2 reduced due to the steric hindrance of methyl and electronic effect. According to the Bader charge, HOMO and LUMO analysis, the adsorption energy of carbazole compounds on MoS2 increased along with increased amount of electrons on N atom. It was observed that the lone pair electrons on N atom of adsorbed pyrrole ring are transferred to the electron-deficient center on Mo atoms, and the LUMO orbit of carbazole compounds accepts electrons in the HOMO orbit of S atoms, leading to the stable adsorption of carbazole compounds on the surface of MoS2.