纳米结构二氧化钛薄膜带隙缺陷态对光电化学性质的影响机制及性能优化

发布时间：2018-04-14 00:06

本文选题：纳米二氧化钛 + 缺陷态　；参考：《烟台大学》2017年硕士论文

【摘要】：最近10年的研究发现,带隙缺陷态是影响纳米结构半导体光电化学性能的主要因素。然而,其影响机制尚不清晰。本文通过研究二氧化钛纳米结构薄膜电极的缺陷态分布以及载流子动力学行为,进而揭示带隙缺陷态对光电催化水分解制氢活性的影响,并基于此指导制备高活性纳米结构二氧化钛光电极薄膜。本文借助场发射扫描电子显微镜(FESEM)和X射线粉末衍射(XRD)技术对样品的纳米结构和形态进行研究;借助电化学交流阻抗谱(EIS)研究缺陷态对半导体载流子传输动力学行为的影响;借助循环伏安法(CV)以及斩光时间电流(I-t)曲线等光电化学测试技术研究样品光电化学性质及缺陷态分布情况,研究内容主要分为以下三个部分:(1)探究二氧化钛纳米颗粒薄膜中的两种常见的缺陷,即表面和晶界缺陷对光电催化活性的破坏作用。为此,我们采用两种不同的烧结机制制备了纳米聚集结构相同但两种缺陷含量不同的二氧化钛薄膜。研究发现晶界缺陷对薄膜的光电化学性能影响更甚,是影响载流子传输动力学以及导致光电化学活性较低的主要原因。(2)在(1)的基础上,深入探究缺陷态对半导体光电化学性质的影响机制。研究发现,缺陷态密度越大,光电流衰减越为严重。本章通过染料吸附、酚酞变色、“Ti-O-P”化学键遇碱水解以及电化学/光电化学等一系列实验,证明被捕获电子与电解质阳离子间存在强的静电吸引作用,导致电子逃逸势垒增大,从而增加了光生载流子的传输阻力以及复合几率,进而引发光电流衰减。(3)基于(1)和(2),借助溶胶凝胶法与水热法制备了单晶二氧化钛纳米棒阵列薄膜,并建立了高温热处理改善光电化学活性的方法。研究表明高温烧结可以显著减少缺陷,从而优化了载流子传输动力学。本文对揭示纳米结构半导体缺陷态对光电化学性质的影响机制以及指导高活性半导体光催化剂和光电极的研制都具有一定的借鉴作用。
[Abstract]:In the last 10 years, it has been found that the band gap defect states are the main factors affecting the photochemical properties of nanostructured semiconductors.However, its influence mechanism is not clear.In this paper, the distribution of defect states and the carrier dynamics of TIO _ 2 nanostructured thin film electrodes are studied, and the effect of the defect states in band gap on the activity of photocatalytic water decomposition to produce hydrogen is revealed.Based on this guidance, highly active nanostructured TIO _ 2 photoelectrode films were prepared.In this paper, the nanostructures and morphology of the samples were studied by means of field emission scanning electron microscopy (FESEM) and X-ray powder diffraction (XRD) techniques, and the effects of defect states on the transport kinetics of semiconductor carriers were studied by electrochemical impedance spectroscopy (EIS).By means of cyclic voltammetry (CV) and chopping time current (I-t) curves, the photoelectric chemical properties and the distribution of defect states of the samples were studied.The research contents are divided into the following three parts: 1) to explore the destruction of photocatalytic activity caused by surface and grain boundary defects in TIO _ 2 nanocrystalline films.Therefore, two different sintering mechanisms were used to prepare TIO _ 2 thin films with the same nano-aggregate structure but different defect contents.It is found that grain boundary defects have a greater effect on the photochemical properties of the films, which is the main reason for the influence of carrier transport kinetics and the lower photochemical activity.The mechanism of the effect of defect states on the photochemical properties of semiconductors is studied in depth.It is found that the higher the density of defect states, the more serious the photocurrent attenuation.In this chapter, a series of experiments, such as dye adsorption, phenolphthalein coloration, "Ti-O-P" chemical bond hydrolysis and electrochemical / photochemistry, show that there is a strong electrostatic attraction between trapped electrons and electrolyte cations.The electron escape barrier increases, which increases the transport resistance and recombination probability of photogenerated carriers, and then leads to photocurrent attenuation. Based on 1) and 2 +, single crystal titanium dioxide nanorod array films are prepared by sol-gel method and hydrothermal method.The method of improving photochemical activity by high temperature heat treatment was established.The results show that high temperature sintering can significantly reduce defects and optimize carrier transport kinetics.This paper can be used for reference in revealing the influence mechanism of the defect states of nanostructured semiconductors on the photochemical properties and guiding the development of highly active semiconductor photocatalysts and photoelectrodes.
【学位授予单位】：烟台大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ134.11;TB383.2

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