【作者】 李赞；

【导师】 吴晓宏；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2016， 博士

【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。更多还原

【Abstract】 Al doped ZnO（AZO）showed excellent electrical and optical performances and is widely used in thermoelectricity,solar cells,gas sensors and photocatalysis.In this work,AZO with exposed specific crystal face and different morphologies were solvothermally synthesized by designing experimental program reasonably.The crystal growth and morphology evolution mechanism of AZO have been revealed.The theoretical basis and technical assistance have been provided for AZO controllable synthesis.Gas sensors based on AZO have been fabricated.The internal ralationship between morphology and gas sensing properties has been studied.The gas-sensing mechanism model has been established.Based on energy band matching theory,metal phthalocyanine complex sensitized AZO photocatalysts have been designed and synthesized.The photocatalytic degradation mechanism has been revealed.The main research content is as follows:AZO were solvothermally synthesized from zinc acetate,aluminum nitrate and HMT by adjusting the reactant concentrations,the ratio of water and ethanol in mixed solvent,additives,the mixing amount of aluminum,additives,the mixing amount of aluminum,reaction temperature and reaction time.The crystal structures,morphologies and chemical constitutions were characterized by XRD,SEM,TEM and HRTEM,XPS and IR respectively.The AZO powders were obtained with seven kinds of morphologies exposed（0001）crystal facet.These morphologies were plates,flowers,dumbbells,cactus,ball-flowers,rice and rods respectively.The as-synthesized AZO powder exposed mainly（0001）plane.According to density functional theory of first-principles the surface energy of AZO was calculated by means of CASTEP software.The results indicated that（0001）surface energy of AZO after reacting with H2 O molecules decreased,and then the law of crystal growth and morphology evolution have been discussed.The indirectly heated gas sensors based on AZO powders have been fabricated.The results revealed that the optimum working temperature is 332 ℃.This kind of AZO gas sensor showed high selectivity and good response-recovery time to ethanol.The influences of morphology and aluminum doping amount on the gas sensitivity have been further studied.The AZO nanoplates exposed more（0001）planes showed excenllent gas sensitivity to ethanol.The AZO nanoplates with 3 at.% Al doping showed good response to ethanol.It’s also found that AZO nanoplates provided most（0001）crystal facets to adsorb maximum ethanol by calculation of CASTEP software of density functional theory in the first principles,thereby AZO gas sensor with plates morphology showed the best selectivity and sensitivity.This is consistent with the experimental results.In order to explore the gas-sensing mechanisms,the research on dynamics has been carried out and the rate equation of gas-sensing reaction has been set up.The reaction order is determined as the first order reaction.The form of oxygen adsorption is O2-.The relationship between AZO sensitivity and the grain size has been discussed.The surface depletion layer model is set up.Better use ratio of visible light and develop efficient photocatalytic material are hot topics in photocatalysis field at present.Energy level matched sensitized AZO photocatalysts were desgined and synthesized in this work.Firstly,Cu Pc（iso-PeO）₈,CoPc（iso-PeO）₈,Ni Pc（iso-Pe O）₈ and Pb Pc（iso-PeO）₈ metal phthalocyanine complex sensitizers and sensitized AZO photocatalysts were synthesized.The photocatalytic performances of sensitized AZO powders in degradation methylene blue have been studied,then it was found that absorption wavelength was red shifted 21 nm after sensitization and the degradation efficiency of sensitized AZO improved by 30%.The influence of sensitizers,morphologies,and the doping amounts of Al on photocatalytic activity were studied respectively.The results indicated that AZO sensitized by PbPc（iso-Pe O）₈,AZO flowers and AZO with 3 at.% Al dopant exhibited better degradation efficiency.In order to explore mechanism of photocatalysis of the sensitizied AZO.The dynamic experiment has been designed.The photocatalytic reaction in degradation methylene blue is confirmed as the pseudo first order reaction.The speed constants are 0.08653 min-1 for flower-like,0.0590 min-1 for plates and 0.0517 min-1 for dumbbell-like,respectively.The spectral analysis of sensitizied AZO indicated that it has type II alternating energy band structure,the light carrier sepa ration has been improved effectively and recombination has been inhibited,a series of degradation reactions triggered by ROS can be realized.更多还原