【摘要】：光催化是光和物質(zhì)相互作用的重要表現(xiàn)形式之一,是指發(fā)生在材料和表面吸附物之間的光反應(yīng)和催化反應(yīng)的復(fù)雜過程。最常用的半導(dǎo)體催化劑是TiO_2,但是TiO_2的禁帶寬度較大,使得光催化氧化只能在紫外光環(huán)境下進(jìn)行反應(yīng)。目前工作的重點(diǎn)是對TiO_2進(jìn)行改性,使其在可見光下也能有較好的光催化效果。國內(nèi)外對TiO_2的改性研究已經(jīng)取得了很大的進(jìn)展,石墨烯作為輔助光催化材料近年來也得到廣泛的關(guān)注,但是對其物理機(jī)理的研究還不夠深入。為此,本文基于密度泛函理論,針對鈦基石墨烯材料光催化氧化氣態(tài)汞的反應(yīng)機(jī)理進(jìn)行深入研究。首先,建立銳鈦礦相TiO_2的晶體模型,基于密度泛函理論,采用從頭計(jì)算法計(jì)算銳鈦礦相TiO_2的能帶結(jié)構(gòu)和電子態(tài)密度�；谏鲜瞿Ｐ蜆�(gòu)建銳鈦礦相TiO_2熱力學(xué)最穩(wěn)定面(101)晶面,研究在該晶面分別摻雜N和Eu元素對能帶結(jié)構(gòu)和電子態(tài)密度的影響,揭示該摻雜對光催化性能的影響的物理機(jī)制。其次,構(gòu)建石墨烯摻雜銳鈦礦相TiO_2模型,在TiO_2(101)面上覆蓋單層石墨烯材料,并分別利用第一動力學(xué)原理和第一性原理對該模型進(jìn)行幾何優(yōu)化,計(jì)算優(yōu)化完成模型的能帶結(jié)構(gòu)和電子態(tài)密度,說明石墨烯摻雜鈦基材料光催化性能改善的物理機(jī)制;在上述模型的基礎(chǔ)之上,構(gòu)建N、Eu和石墨烯混摻鈦基材料,研究N和Eu的摻雜對Gr/TiO_2能帶結(jié)構(gòu)的影響。結(jié)果表明混摻情況下材料的光催化活性最高。最后,為驗(yàn)證上述計(jì)算結(jié)果的準(zhǔn)確性,利用水熱反應(yīng)法制備銳鈦礦相TiO_2,調(diào)節(jié)制備條件,使材料主要暴露面為(101)晶面。對制備完成的材料進(jìn)行SEM、XRD、UV-Vis和BET表征。同時,利用曲面積分法探究不同摻雜對光催化脫汞性能的影響,進(jìn)一步證明上述模型計(jì)算結(jié)果的正確性,并確定材料的最佳制備條件。通過計(jì)算材料的結(jié)果和實(shí)驗(yàn)結(jié)果進(jìn)行對比,成功驗(yàn)證計(jì)算結(jié)果的可靠性,為鈦基材料改性的理論研究提供了支持。
[Abstract]:Photocatalysis is one of the important forms of interaction between light and matter, which refers to the complex process of photoreaction and catalytic reaction between material and surface adsorbents. The most commonly used semiconductor catalyst is TiO_2, but the band gap of TiO_2 is large, so that photocatalytic oxidation can only react in UV environment. At present, the focus of the work is to modify TiO_2 so that it can also have a good photocatalytic effect under visible light. Great progress has been made in the modification of TiO_2 at home and abroad. Graphene as an auxiliary photocatalysis material has also received extensive attention in recent years, but the physical mechanism of graphene is not deep enough. In this paper, based on density functional theory (DFT), the mechanism of photocatalytic oxidation of gaseous mercury by graphene, the cornerstone of titanium, was studied. Firstly, the crystal model of anatase phase TiO_2 is established. Based on density functional theory, the band structure and electronic state density of anatase phase TiO_2 are calculated by ab initio method. Based on the above model, the thermodynamic most stable surface of anatase phase TiO_2 was constructed, and the effects of N and Eu elements on the energy band structure and electronic state density were studied. The physical mechanism of the effect of the doping on the photocatalytic performance was revealed. Secondly, the graphene-doped anatase phase TiO_2 model is constructed, and the monolayer graphene material is covered on the TiO_2 surface, and the geometric optimization of the model is carried out by using the first kinetic principle and the first principle, respectively. The energy band structure and electronic state density of the model are calculated and optimized, which shows the physical mechanism of improving the photocatalytic performance of graphene-doped titanium-based materials. On the basis of the above model, N, EU and graphene mixed titanium-based materials were constructed, and the effect of N and Eu doping on the energy band structure of Gr/TiO_2 was studied. The results show that the photocatalytic activity of the material is the highest under the condition of mixing. Finally, in order to verify the accuracy of the above calculation results, anatase phase TiO_2, was prepared by hydrothermal reaction method to adjust the preparation conditions, so that the main appearance of the material was (101) crystal plane. The prepared materials were characterized by SEM,XRD,UV-Vis and BET. At the same time, the effect of different doping on photocatalytic mercury removal performance was studied by surface integration method, which further proved the correctness of the calculated results of the above model, and determined the optimum preparation conditions of the material. By comparing the calculated results with the experimental results, the reliability of the calculated results is successfully verified, which provides support for the theoretical study of the modification of titanium-based materials.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O643.3

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