掺铝氧化锌的可控合成及其气敏和光催化性能研究

发布时间：2018-05-31 00:43

  本文选题：掺铝氧化锌 + 溶剂热法　； 参考：《哈尔滨工业大学》2016年博士论文

【摘要】：掺铝氧化锌(AZO)具有优异的电学和光学等性能,被广泛应用在热电、太阳能电池、气敏和光催化等领域。本文采用溶剂热法,通过合理设计实验方案,得到以暴露特定晶面为主的形貌各异的AZO粉体,揭示了AZO晶体生长及形貌演变机制,为AZO材料的可控合成提供理论基础和技术支持。基于AZO粉体制作了气敏元件,研究AZO形貌和结构与气敏特性的内在关系,建立气敏机制模型。基于能带匹配理论,设计并合成金属酞菁配合物敏化AZO光催化剂,研究其能带结构对光催化性能的影响,揭示了光催化降解机制。主要研究内容如下:以乙酸锌为锌源,硝酸铝为铝源,六亚甲基四胺为碱源,采用溶剂热法,通过改变反应物浓度、水和乙醇混合溶剂的配比、添加剂种类、掺铝量、反应时间和反应温度,合成出不同形貌的AZO粉体,利用XRD、SEM、TEM和HRTEM、XPS、IR等分析其晶体结构、形貌和化学组成等,得到了以暴露(0001)晶面为主的7种不同形貌的AZO粉体,分别为片状、花朵状、哑铃状、仙人掌状、花球状、米粒状及棒状。基于第一性原理密度泛函理论,利用CASTEP软件包对ZnO的表面能进行了计算,发现其(0001)晶面吸附水分子后表面能降低,基于此结果,探究晶体生长过程和形貌演变规律。将AZO粉体制作成旁热式气体传感器,结果发现最佳工作温度为332℃,对乙醇具有高选择性,对乙醇的响应恢复性能好;研究AZO形貌和铝的掺杂量对气敏性能的影响,发现暴露大量(0001)晶面的片状AZO和铝掺杂量为3 at.%时气敏性能最佳。基于第一性原理密度泛函理论,计算得到,片状AZO提供最多的(0001)晶面以吸附最大量乙醇分子,从而表现出对乙醇气体的高选择性和灵敏性,这与气敏性能的实验结果相一致。为探究AZO气敏机制,进行了动力学实验并建立气敏反应的速率方程,其吸附反应为准一级反应,确定吸附形式是O2-。研究了AZO灵敏度与晶粒尺寸的关系,建立AZO的表面耗尽层模型。提高可见光利用率和开发高效光催化材料是目前光催化领域的热点问题。本论文设计并合成能级匹配的敏化AZO光催化剂。首先成功合成4种金属酞菁配合物敏化剂(Cu Pc(iso-PeO)_8、CoPc(iso-PeO)_8、Ni Pc(iso-PeO)_8和Pb Pc(isoPeO)_8)和敏化AZO光催化剂。研究敏化AZO光催化降解亚甲基蓝的效率,发现敏化使AZO的吸收波长红移21 nm,其光催化活性提高约30%。分别研究了敏化剂种类、AZO形貌及掺铝量对光催化降解亚甲基蓝的影响,发现PbPc(iso-PeO)_8敏化剂、花朵状形貌和3 at.%掺铝量的影响最大。为探究敏化AZO的光催化机制,设计了动力学实验,确定光催化降解亚甲基蓝的反应为准一级反应,速率系数k分别为0.08653 min-1(花朵状)、0.0590 min-1(片状)和0.0517 min-1(哑铃状)。对敏化AZO的光谱分析表明它具有type II交错式能带结构,这有效改善了光生载流子的分离并抑制其复合,能够实现ROS引发的一系列光降解反应。
[Abstract]:Aluminum-doped zinc oxide (AZO) has been widely used in thermoelectricity, solar cells, gas sensing and photocatalysis due to its excellent electrical and optical properties. In this paper, AZO powders with different morphologies are obtained by using solvothermal method and reasonable design of experimental scheme. The mechanism of AZO crystal growth and morphology evolution is revealed. It provides theoretical basis and technical support for controllable synthesis of AZO materials. Based on the AZO powder, the gas sensing elements were fabricated. The relationship between the morphology and structure of AZO and the gas sensing characteristics was studied, and the gas sensing mechanism model was established. Based on the energy band matching theory, the metal phthalocyanine complexes sensitized AZO photocatalysts were designed and synthesized. The influence of the band structure on the photocatalytic performance was studied, and the photocatalytic degradation mechanism was revealed. The main contents are as follows: zinc acetate as zinc source, aluminum nitrate as aluminum source, hexamethylenetetramine as base source, solvothermal method, by changing the concentration of reactants, the mixture ratio of water and ethanol, the type of additives, the amount of aluminum, AZO powders with different morphologies were synthesized by reaction time and reaction temperature. The crystal structure, morphology and chemical composition of AZO powders with different morphologies were analyzed by XRDD-SEMMA-TEM and HRTEM-XPS-IR, respectively. Seven kinds of AZO powders with different morphologies were obtained, respectively, which were flaky. Flower-shaped, dumbbell-shaped, cactus-shaped, flower globular, rice-shaped and rod-shaped. Based on the first-principle density functional theory, the surface energy of ZnO was calculated by using CASTEP software package. It was found that the surface energy of ZnO adsorbed on the crystal surface was decreased. Based on the results, the law of crystal growth process and morphology evolution was investigated. The AZO powder was prepared into a side heat gas sensor. The results show that the optimum working temperature is 332 鈩，

本文编号：1957576