本文關鍵詞： 原子級厚二維結構 構效關系 二氧化碳還原 光電解水　出處：《中國科學技術大學》2017年博士論文　論文類型：學位論文

【摘要】：全球變暖與化石能源大量開采使用息息相關,人類社會的快速發(fā)展對能源需求持續(xù)快速增長,目前化石燃料仍占全球能源消費的80%,建立在不可重復利用的化石能源基礎上的傳統(tǒng)能源發(fā)展方式難以為繼。解決能源危機和溫室效應的根本出路是開發(fā)新能源、構建全球能源互聯(lián)網(wǎng),加快綠色能源替代,實現(xiàn)綠色能源大規(guī)模開發(fā)、高效率利用,從根本上解決化石能源污染和溫室氣體排放問題。為了實現(xiàn)更有效、更環(huán)保的能源利用,針對太陽能、氫能以及二氧化碳還原為碳氫燃料能源的開發(fā),有利于建造一個清潔、高效、可持續(xù)的全球能源網(wǎng)絡。而在眾多已發(fā)展的光電解水、二氧化碳還原半導體催化劑中,原子級厚二維結構催化劑因其特殊的原子結構、電子結構特征,以及因為原子的缺失引入的缺陷結構等特征,被認為是光電解水、二氧化碳還原催化劑的有利候選者。本論文以原子級厚二維材料為研究對象,以宏觀功能(光還原二氧化碳、電解水及光電解水)與微觀結構(原子結構、電子結構和缺陷結構)之間內(nèi)在關系為主線,旨在揭示原子級厚二維材料宏觀性質(zhì)與其微觀結構之間的構效關系,深化對原子級厚二維材料宏觀性能和結構本質(zhì)的認識,為實現(xiàn)原子級厚二維材料功能導向的結構設計和可控制備提供新思路、新方法和新材料體系。本論文對具有應用前景的功能原子級厚二維材料的進行設計,補充及發(fā)展了可控制備方法以及表征手段,對宏觀功能進行探索研究,從原子級尺度上揭露了原子級厚二維材料宏觀功能與微觀結構之間的關系。本論文主要研究內(nèi)容如下:1.我們首次構建了一個原子級厚二維半導體的結構模型,它能提供豐富的催化活性位點,具有良好的二維電導率和優(yōu)越的結構穩(wěn)定性。我們通過制備Bi-油酸根層狀雜化中間體得到正交相鎢酸鉍二維超薄結構。二維超薄結構使更多的內(nèi)部原子暴露在表面,不僅有利于增加二氧化碳的吸附量,還有助于獲得更高的光吸收能力。第一性原理計算顯示二維超薄結構具有顯著增加的態(tài)密度,進而有利于載流子傳輸。時間分辨熒光光譜顯示二維超薄結構有利于電子-空穴的分離,進而促使光還原二氧化碳性能得到提升,為設計高效的光催化還原二氧化碳催化劑提供了新的思路。2.我們首次構建了一個具有金屬性的非金屬物質(zhì)的原子級厚二維結構模型。以CoSe_2為例,通過制備CoSe_2-DETA(二乙烯三胺)層狀雜化中間體得到正交相CoSe_2單胞厚二維結構。密度泛函理論計算和變溫電導率測試均證實原子級厚正交相CoSe_2二維結構具有金屬性的導電行為。同步輻射X射線吸收精細結構譜表明,相對于塊材,原子級厚CoSe_2二維結構表面鈷原子的配位數(shù)明顯降低,這有利于提高其本征催化活性�；诖�,原子級厚CoSe_2二維結構表現(xiàn)出相較于CoSe_2-DETA層狀雜化中間體和塊材更高的電流密度、更低的Tafel斜率和更高的轉(zhuǎn)換頻率(TOF),進而獲得更好的電解水性能。3.我們建構了一個可控厚度的p型半導體納米片模型,研究其厚度與光電解水性能之間的關系。首先通過簡單的液相剝離法得到不同厚度的超薄氧化亞錫二維結構。氧化亞錫二維結構厚度越薄,比表面積越大,提供的活性位點越多,同時通過第一性原理計算得知相較于氧化亞錫塊材,超薄氧化亞錫二維結構費米能級附近的態(tài)密度增強,提高了載流子的分離效率,從而獲得高的可見光光轉(zhuǎn)化效率。光電解水實驗結果表明,3 nm厚的超薄氧化亞錫二維結構具有相對較高的光電轉(zhuǎn)化效率,揭示了超薄p型半導體納米片的厚度與光電解水分解效率的關系。
[Abstract]:Global warming and a large number of fossil energy exploitation is closely related to the rapid development of human society to the sustained and rapid growth in energy demand, the current fossil fuel still accounts for 80% of global energy consumption, the traditional energy development mode establishment in the repeated use of fossil energy on the basis of hard to continue. The fundamental way to solve the energy crisis and the greenhouse effect is developed new energy, building global energy Internet, accelerate the implementation of large-scale development of alternative green energy, green energy, efficient use of fossil energy, solve the problem of pollution and greenhouse gas emissions fundamentally. In order to achieve more efficient, more environmentally friendly energy utilization, for solar energy, hydrogen and carbon dioxide reduction for the development of hydrocarbon fuel energy, is conducive to the construction of a a clean, efficient and sustainable global energy network. And has developed in many photoelectric semiconductor solutions of water, carbon dioxide reduction In the catalyst, the atomic structure of two-dimensional thick catalyst because of its special characteristics of atomic structure, electronic structure, and because of lack of the defects induced by atomic structure characteristics, considered photoelecirolysis water, favorable candidates for reduction of carbon dioxide catalyst. The atomic level thick two-dimensional material as the research object, to the macro function (light reduction carbon dioxide, water electrolysis and photoelecirolysis water) and microstructure (electronic structure and defect structure of atomic structure, the intrinsic relationship between) as the main line, in order to reveal the relationship between the macroscopic properties of atomic thick two-dimensional material and its microstructure, deepen understanding of the macroscopic properties of atomic thick two-dimensional materials and structural nature, structure design the atomic level thick two-dimensional material function oriented and controllable preparation to provide new ideas, new methods and new materials system. This paper has the application prospect of the function of atomic level The design of thick two-dimensional materials, supplementary and the development of the controllable preparation method and characterization method, studies the macro function, from the atomic scale reveals the relationship between the macro function of atomic thickness and microstructure of two-dimensional materials. The main research contents of this paper are as follows: 1. we first constructed an atomic level the thickness of two-dimensional semiconductor structure model, it can provide the catalytic active sites rich, has good conductivity and excellent dimensional stability. We prepared Bi- structure of oleate layered hybrid system get through intermediate orthorhombic structure. Two dimensional 2D thin bismuth tungstate thin structure make more atoms exposed on the surface, not only conducive to the increase of adsorption capacity carbon dioxide, also helps to obtain higher light absorption ability. The first principle calculations show that the two-dimensional ultrathin structure has significantly increased the density of States, and For carrier transport. Time resolved fluorescence spectra display two-dimensional ultrathin structure is conducive to the separation of electron hole, and then promote the light reduction of carbon dioxide to improve the performance, for the design of efficient photocatalytic reduction of carbon dioxide catalyst provides a new idea of.2. for the first time we build the atomic level thick two-dimensional structure model with a metal non metal material. In the case of CoSe_2, the preparation of CoSe_2-DETA by (two three ethylene amine) layered hybrid intermediate orthorhombic CoSe_2 single cell thick two-dimensional structure. Density functional theory calculation and variable temperature conductivity test were confirmed the electrical behavior of atomic thick orthorhombic CoSe_2 two-dimensional structure with metallic. Synchrotron radiation X ray absorption fine structure spectra show that relative to the bulk coordination number of atomic level surface cobalt atoms thick CoSe_2 two-dimensional structure is significantly reduced, which is beneficial to improve the intrinsic catalytic activity. At the atomic level CoSe_2 thick two-dimensional structure show compared to the current density of CoSe_2-DETA layered hybrid intermediate and bulk higher Tafel, lower slope and higher switching frequency (TOF), electrolysis of water and get better performance of.3., we construct a p type semiconductor nano sheet model of a controllable thickness and its research the thickness and relationship between the performance of photoelecirolysis water. First, by a simple liquid phase separation method by thin SnO two-dimensional structure with different thickness. The thickness of tin oxide two-dimensional structure thinner, larger specific surface area, active site provides more, at the same time by first principle calculation that compared to the bulk of stannous oxide the density of state, near the thin SnO two-dimensional structure of Fermi level enhancement, to improve the separation efficiency of the carrier, so as to obtain high visible light photoelectric conversion efficiency. The experimental results show that the solution of water, 3 nm thick The two-dimensional structure of ultra-thin tin oxide has relatively high photoelectric conversion efficiency, revealing the relationship between the thickness of ultra-thin P semiconductor nanosheets and the efficiency of photoelectric decomposition of water.

【學位授予單位】：中國科學技術大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O643.36

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