碱金属改性g-C_3N_4及其对氮气吸附影响的理论研究  

Theoretical Study of Alkali Metal Modified g-C_3N_4 and Its Influence on Nitrogen Adsorption

作　　者：李强[1] 李晴[1,2] 吕扬 王焕 秦玉才[1] 宋丽娟 胡绍争[1] Li Qiang;Li Qing;Lü Yang;Wang Huan;Qin Yucai;Song Lijuan;Hu Shaozheng(Liaoning Provincial Key Laboratory of Petrochemical Catalytic Science and Technology,Liaoning Shihua University,Fushun Liaoning 113001,China;Enhanced Oil Recovery Institute,China University of Petroleum（Beijing）,Beijing 102249,China;College of Chemical Engineering,China University of Petroleum（East China）,Qingdao Shandong 266580,China)

机构地区：[1]辽宁石油化工大学辽宁省石油化工催化科学与技术重点实验室,辽宁抚顺113001 [2]中国石油大学(北京)提高采收率研究院,北京102249 [3]中国石油大学(华东)化学工程学院,山东青岛266580

出　　处：《辽宁石油化工大学学报》2018年第6期37-42,共6页Journal of Liaoning Petrochemical University

基　　金：辽宁省自然科学基金指导计划项目(201602467);辽宁石油化工大学引进人才科研启动基金项目(2016XJJ-016)

摘　　要：研究了碱金属改性对g-C_3N_4光催化剂的影响,利用密度泛函理论从几何和电子结构的角度阐述了不同碱金属改性对提高光催化活性的微观机理。结果表明,Li、Na、K、Rb原子随着核外电子层数的增加,碱金属和g-C_3N_4的结合能越来越弱,对g-C_3N_4结构的影响也越来越弱。电子结构分析可知,Li、Na、K原子对g-C_3N_4具有活化作用,Rb原子对g-C_3N_4表面有钝化作用。同时模拟了N_2分子在M-g-C_3N_4(M=Li、Na、K、Rb)上的吸附,理解N_2分子与碱金属之间的作用机理,通过分析N_2吸附的吸附能、结构参数和电子特性,发现Li、Na原子对N_2吸附的影响更大,N_2的N—N键长伸长,K和Rb原子对N_2基本没有作用。碱金属改性g-C_3N_4比纯g-C_3N_4更有利于N_2分子的吸附,但是随着碱金属原子半径的增加,吸附能力越来越弱,电子的转移也越来越少,即活化N_2分子的能力按照Li、Na、K、Rb的顺序降低。The effect of alkali metal modification on g-C 3N 4 photocatalyst was systematically studied. The density functional theory is used to explain the microscopic mechanism of different alkali metal modification on improving photocatalytic activity from the various angles of geometry and electronic structure. The results show that the binding energies of alkali metals and g-C 3N 4 become weaker and weaker with the increase of the number of extra-nuclear electronic layers of Li, Na, K and Rb atoms, and the influence on the structure of g-C 3N 4 is weaker and weaker. The electronic structure analysis shows that Li, Na, and K atoms have an activation effect on g-C 3N 4, and Rb atoms have a passivation effect on the surface of g-C 3N 4. At the same time, the adsorption of N 2 molecules on M-g-C 3N 4 （M=Li, Na, K, Rb） is simulated, and the interaction mechanism between N 2 molecules and alkali metals is understood. By analyzing the adsorption energy, structural parameters and electronic properties of N 2 adsorption, it is found that the influence of Li and Na atoms on N 2 adsorption is greater. The N—N bond of N 2 is elongated, and the K and Rb atoms have little effect on N 2. Alkali metal modified g-C 3N 4 is more beneficial for the adsorption of N 2 molecules than pure g-C 3N 4, but as the atomic radius of the alkali metal increases, the adsorption capacity becomes weaker and weaker, and the electron transfer becomes less and less. That is to say, the ability of activating N 2 molecule decreases in the order of Li, Na, K and Rb.

关 键 词：密度泛函理论 g-C3N4 碱金属改性 氮气吸附 

分 类 号：O643.31[理学—物理化学]