含過(guò)渡元素LDHs的電子結(jié)構(gòu)及可見光催化性能第一性原理研究
發(fā)布時(shí)間：2018-11-05 13:18
【摘要】：由于層狀雙金屬氫氧化物(LDHs)具有層板金屬元素的可替換性、原子級(jí)均勻分散性等特點(diǎn)使之成為光催化的研究熱點(diǎn)。本文采用密度泛函理論的第一性原理計(jì)算,對(duì)部分含過(guò)渡元素的LDHs的電子結(jié)構(gòu)進(jìn)行計(jì)算,探討含過(guò)渡元素LDHs中層板金屬元素、表面缺陷位點(diǎn)及其復(fù)合材料等因素和可見光催化性能的關(guān)系,為構(gòu)筑新型高分散催化劑提供了一定的理論基礎(chǔ)。主要?jiǎng)?chuàng)新性研究?jī)?nèi)容及結(jié)論包括：1、根據(jù)LDHs層板金屬元素的可替換性,將Zn、Ti等過(guò)渡元素和常見的LDHs替換,使得TiO6等基元在LDHs介質(zhì)中高度分散,解決了傳統(tǒng)催化劑在應(yīng)用過(guò)程中活性組分易團(tuán)聚、分散度低的問題。同時(shí)發(fā)現(xiàn),過(guò)渡元素調(diào)節(jié)了LDHs的禁帶寬度,可對(duì)太陽(yáng)光中的可見光部分響應(yīng),Mm+或Nn+對(duì)LDHs催化性能的影響程度取決于M、N金屬元素本身。同時(shí),OH=基團(tuán)易捕獲空穴而產(chǎn)生自由基,LDHs表面的OH基團(tuán)有效地提升了載流子的傳輸效率。2、通過(guò)建立含H和OH缺陷位點(diǎn)的LDHs模型,探討不同價(jià)態(tài)的Mm+或Nn+對(duì)可見光催化分解H2O性能的影響。結(jié)果表明,不同價(jià)態(tài)的Mm+或Nn+元素對(duì)光催化性能有一定影響,H或OH缺陷位點(diǎn)作為光生e-的受限位抑制了e-和h+復(fù)合,使得更多的e-和h+參與氧化還原反應(yīng)中,從而使得可見光催化性能進(jìn)一步提升。3、通過(guò)建立LDHs-X(X:石墨烯、還原氧化石墨烯、TiO2、g-C3N4)復(fù)合模型,采用第一性原理計(jì)算探討LDHs復(fù)合材料催化劑的催化性能。結(jié)果表明,LDHs與還原氧化石墨烯、TiO2、g-C3N4等通過(guò)氫鍵或者C-0-M鍵連接,形成了電子遷移的通道。LDHs與還原氧化石墨烯、TiO2、g-C3N4等的能帶差異和氧化還原電位錯(cuò)位,造就異質(zhì)結(jié),使得LDHs光激發(fā)的電子通過(guò)兩者間的氫鍵或者C-0-M鍵遷移到還原氧化石墨烯、TiO2、g-C3N4等基材上,減少e-和h+復(fù)合,從而提升了光催化性能。
[Abstract]:Layered bimetallic hydroxide (LDHs) has become a hotspot in photocatalysis due to its substitutability of metal elements in laminates and the homogeneity of atomic dispersion. In this paper, the first principle calculation of density functional theory is used to calculate the electronic structure of LDHs with transition elements, and the laminated metal elements in LDHs with transition elements are discussed. The relationship between the surface defect sites and their composite materials and their visible light catalytic properties provides a theoretical basis for the construction of novel highly dispersed catalysts. The main innovative research contents and conclusions are as follows: 1. According to the substitutability of metal elements in LDHs laminates, the transition elements such as Zn,Ti and common LDHs are replaced, so that TiO6 and other elements are highly dispersed in LDHs medium. The problem of easy agglomeration and low dispersity of active components in the application of traditional catalysts was solved. It is also found that the transition element adjusts the band gap of LDHs and can respond to the visible light in the solar light. The influence of Mm or Nn on the catalytic performance of LDHs depends on the metal element Mon itself. At the same time, the OH= group is easy to capture holes and produce free radicals, and the OH group on the LDHs surface can effectively improve the transport efficiency of carriers. 2. By establishing the LDHs model with H and OH defect sites, The effect of Mm or Nn in different valence states on the catalytic decomposition of H2O by visible light was investigated. The results show that different valence elements of Mm or Nn have a certain effect on photocatalytic performance. The defect sites of H or OH, as the restricted sites of photogenerated e-, inhibit the combination of e- and h, and make more e- and h participate in the redox reaction. Thus, the catalytic performance of visible light was further improved. 3. By establishing LDHs-X (X: graphene, reduced graphene, TiO2,g-C3N4) composite model, the first principle calculation was used to study the catalytic performance of LDHs composite catalyst. The results show that LDHs is connected with reduced graphene oxide and TiO2,g-C3N4 by hydrogen bond or C-0-M bond to form electron transport channel. LDHs is associated with reduced graphene oxide, TiO2, and so on. The energy band difference of g-C3N4 and the dislocation of redox potential make the photoexcited electrons of LDHs migrate to the reduced graphene, TiO2,g-C3N4 and other substrates through the hydrogen bond or C-0-M bond between them. The photocatalytic performance was improved by reducing the composition of e- and h.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：O611.2;O643.3
本文編號(hào)：2312208
[Abstract]:Layered bimetallic hydroxide (LDHs) has become a hotspot in photocatalysis due to its substitutability of metal elements in laminates and the homogeneity of atomic dispersion. In this paper, the first principle calculation of density functional theory is used to calculate the electronic structure of LDHs with transition elements, and the laminated metal elements in LDHs with transition elements are discussed. The relationship between the surface defect sites and their composite materials and their visible light catalytic properties provides a theoretical basis for the construction of novel highly dispersed catalysts. The main innovative research contents and conclusions are as follows: 1. According to the substitutability of metal elements in LDHs laminates, the transition elements such as Zn,Ti and common LDHs are replaced, so that TiO6 and other elements are highly dispersed in LDHs medium. The problem of easy agglomeration and low dispersity of active components in the application of traditional catalysts was solved. It is also found that the transition element adjusts the band gap of LDHs and can respond to the visible light in the solar light. The influence of Mm or Nn on the catalytic performance of LDHs depends on the metal element Mon itself. At the same time, the OH= group is easy to capture holes and produce free radicals, and the OH group on the LDHs surface can effectively improve the transport efficiency of carriers. 2. By establishing the LDHs model with H and OH defect sites, The effect of Mm or Nn in different valence states on the catalytic decomposition of H2O by visible light was investigated. The results show that different valence elements of Mm or Nn have a certain effect on photocatalytic performance. The defect sites of H or OH, as the restricted sites of photogenerated e-, inhibit the combination of e- and h, and make more e- and h participate in the redox reaction. Thus, the catalytic performance of visible light was further improved. 3. By establishing LDHs-X (X: graphene, reduced graphene, TiO2,g-C3N4) composite model, the first principle calculation was used to study the catalytic performance of LDHs composite catalyst. The results show that LDHs is connected with reduced graphene oxide and TiO2,g-C3N4 by hydrogen bond or C-0-M bond to form electron transport channel. LDHs is associated with reduced graphene oxide, TiO2, and so on. The energy band difference of g-C3N4 and the dislocation of redox potential make the photoexcited electrons of LDHs migrate to the reduced graphene, TiO2,g-C3N4 and other substrates through the hydrogen bond or C-0-M bond between them. The photocatalytic performance was improved by reducing the composition of e- and h.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：O611.2;O643.3
【參考文獻(xiàn)】
相關(guān)期刊論文 前2條
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，本文編號(hào)：2312208
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