本文選題：TiO_2(101)表面 + 共摻�。� 參考：《昆明理工大學(xué)》2017年碩士論文

【摘要】：銳鈦礦相Ti02是一種典型的寬帶隙的半導(dǎo)體,只能對(duì)紫外光產(chǎn)生響應(yīng),而對(duì)可見光部分不能吸收,導(dǎo)致對(duì)太陽(yáng)能的利用率較低。Ti02的光生電子和空穴都不穩(wěn)定,很容易復(fù)合,光量子效率低。這兩個(gè)方面的問題極大地限制了 Ti02在光催化方面的應(yīng)用。為了解決這些問題,對(duì)Ti02進(jìn)行改性作為一種有效的手段已被廣泛研究。大多數(shù)的催化反應(yīng)都是發(fā)生在材料的表面,對(duì)表面進(jìn)行摻雜以改善表面電子結(jié)構(gòu)獲得與可見光相匹配的TiO2表面更是光催化研究中的一個(gè)熱點(diǎn)。為了探索銳鈦礦相Ti02摻雜改性的機(jī)理,進(jìn)一步改善其在可見光區(qū)的光催化活性,本文通過密度泛函計(jì)算研究了 C/Fe摻雜銳鈦礦相TiO2(101)表面的電子結(jié)構(gòu)和光學(xué)性能。同時(shí),還研究了不同摻雜方式和位置對(duì)Ti02(101)表面各項(xiàng)性能的影響。常規(guī)密度泛函理論是一個(gè)很有效的研究工具,但總是低估帶隙。采用DFT+U的方法有可能克服這一缺陷,但需要引入?yún)?shù)U,而U值的確定卻不容易,因?yàn)槠渑c化學(xué)環(huán)境有關(guān)。鑒于此,我們采用高斯09中基于高斯型軌道的HSE06雜化泛函和6-31G基組描述Ti02表面的電子結(jié)構(gòu)和性質(zhì),特別是帶隙,并且不需要引入任何經(jīng)驗(yàn)參數(shù)。C摻雜后,銳鈦礦相Ti02(101)表面結(jié)構(gòu)發(fā)生一定程度的畸變,并且間隙摻雜引起的結(jié)構(gòu)畸變程度比替位摻雜產(chǎn)生的畸變程度大。摻雜表面在還原條件下表現(xiàn)出相對(duì)較高的穩(wěn)定性,并且當(dāng)C替代二配位的橋位02c時(shí),結(jié)構(gòu)最為穩(wěn)定。C替位摻雜后引入深雜質(zhì)能級(jí),很容易成為電子-空穴對(duì)的復(fù)合中心。C間隙摻雜結(jié)構(gòu)中引入淺雜質(zhì)能級(jí),并能產(chǎn)生可見光響應(yīng),從而改善銳鈦礦相TiO2(101)表面在可見光區(qū)的光催化活性。Fe摻雜銳鈦礦相TiO2(101)表面更容易在氧化條件下合成,其中,Fe替位五配位Ti5c的摻雜結(jié)構(gòu)最容易被合成。替位摻雜后,帶隙幾乎沒有變化,并在帶隙中間引入深雜質(zhì)能級(jí),不能有效改善表面的光催化活性。間隙摻雜后,雜質(zhì)能級(jí)出現(xiàn)在價(jià)帶頂和導(dǎo)帶底,并與價(jià)帶頂和導(dǎo)帶底發(fā)生耦合,促使帶隙減小,使光吸收帶邊發(fā)生一定程度的紅移。此外,還有效促進(jìn)了光生電子-空穴對(duì)的分離,故Fe間隙摻雜的結(jié)構(gòu)能夠改善銳鈦礦相TiO2(101)表面在可見光區(qū)的光催化活性。共摻結(jié)構(gòu)在氧化條件下表現(xiàn)出相對(duì)較高的穩(wěn)定性。Fe5cC2c結(jié)構(gòu)的形成能最低,也最容易被合成。由于協(xié)同作用,雜質(zhì)能級(jí)同時(shí)出現(xiàn)在導(dǎo)帶底和價(jià)帶頂,表現(xiàn)出優(yōu)于單摻的獨(dú)特的電子結(jié)構(gòu)。Fe5cC2c和Fe6cC2c兩種結(jié)構(gòu)中,雜質(zhì)能級(jí)分別與導(dǎo)帶和價(jià)帶耦合,不僅導(dǎo)致了帶隙的減小,使光吸收帶邊明顯紅移,而且還能有效地抑制光生電子-空穴對(duì)的復(fù)合。這樣既產(chǎn)生了對(duì)可見光的響應(yīng),又大大提高了光量子效率,從而有效提高Ti02在可見光區(qū)的光催化活性。
[Abstract]:The anatase phase Ti02 is a typical wide band gap semiconductor, which can only respond to ultraviolet light, but can not be absorbed to the visible light, resulting in the low utilization of solar energy. The photogenerated electrons and holes are unstable and can be easily recombined. The quantum efficiency of light is low. These two problems greatly limit the application of Ti02 in photocatalysis. In order to solve these problems, Ti02 modification as an effective means has been widely studied. Most of the catalytic reactions occur on the surface of the material, and doping the surface to improve the electronic structure of the surface to improve the surface of TiO2 surface matching with visible light is a hot spot in the research of photocatalysis. In order to explore the mechanism of doping modification of anatase phase Ti02 and further improve its photocatalytic activity in visible light region, the electronic structure and optical properties of C / Fe doped anatase phase TIO _ 2 / 101) surface have been studied by density functional calculation (DFT). At the same time, the effects of different doping modes and positions on the properties of Ti02C101) surface were studied. Conventional density functional theory (DFT) is an effective tool, but the band gap is always underestimated. It is possible to overcome this defect by using the DFT U method, but it is necessary to introduce the parameter U, but the determination of U value is not easy because it is related to the chemical environment. In view of this, we use HSE06 hybrid functional and 6-31G basis set based on Gao Si type orbital in Gao Si 09 to describe the electronic structure and properties of Ti02 surface, especially the band gap, and we do not need to introduce any empirical parameter. The surface structure of anatase Ti _ (02) O _ (101) is distorted to a certain extent, and the distortion caused by gap doping is greater than that by substitution doping. The doping surface exhibits relatively high stability under the condition of reduction, and when C replaces the bridge 02c with two coordination sites, the structure is most stable and the deep impurity level is introduced after doping. It is easy to introduce shallow impurity energy levels into the composite center. C gap doping structure of electron-hole pair, which can produce visible light response. Therefore, the photocatalytic activity of anatase phase TIO _ 2O _ (10 ~ (1) surface in visible region is improved. Fe doped anatase phase TIO _ (2) O _ (10 _ (101) surface is easier to be synthesized under oxidation conditions, and the doping structure of Fe substituted five-coordination Ti _ (5c) is the most easily synthesized. After the substitution doping, the band gap is almost unchanged, and the deep impurity energy level is introduced in the middle of the band gap, which can not effectively improve the photocatalytic activity of the surface. After gap doping, the impurity energy levels appear at the top of the valence band and the bottom of the conduction band, and coupled with the top of the valence band and the bottom of the conduction band, which makes the band gap decrease and the absorption band edge red shift to a certain extent. In addition, the separation of photogenerated electron-hole pairs is promoted effectively, so the structure of Fe interstitial doping can improve the photocatalytic activity of anatase phase TIO _ 2O _ (101) surface in visible region. The codoped structure shows relatively high stability under oxidation condition. The formation energy of Fe _ 5c C _ 2c structure is the lowest, and it is the easiest to be synthesized. Due to the synergistic effect, the impurity energy levels appear at the bottom of the conduction band and the top of the valence band at the same time, showing that the impurity level is superior to the unique electronic structure. Fe5cC2c and Fe6cC2c, the impurity level is coupled with the conduction band and the valence band, respectively, which not only leads to the decrease of the band gap. The red shift of the light absorption band edge is obvious, and the recombination of photogenerated electron-hole pair can also be effectively inhibited. In this way, the photocatalytic activity of Ti02 in the visible region can be improved effectively by both the response to visible light and the quantum efficiency of light.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ134.11;O643.36

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