【作者】 张维光；

【导师】 陆路德；

【作者基本信息】 南京理工大学 ， 化学工程与技术， 2009， 博士

【摘要】 ABO₃钙钛矿结构复合氧化物具有多种独特的物理和化学性质,发现和探索这些独特性质的研究工作一直被人们所关注。本文以具有组成多样和性质可调变的ABO₃钙钛矿复合氧化物为研究对象,以其结构特点为基础,以A位和B位掺杂为途径,采用固相法和软化学法,制备了具有光催化活性和光致变色性质的ABO₃钙钛矿结构复合氧化物,研究其结构、组成、表面形态与性能的关系,探索了掺杂银钙钛矿结构复合氧化物修饰电极的电化学发光性质。主要内容如下:用硬脂酸法制备了比表面大、粒径小的AFeO₃（A=Ce、Pr、Nd、Sm、Gd、Dy、Er、Y）和ANiO₃（A=Nd、Gd）系列钙钛矿结构复合氧化物。以亚甲基兰为探针,研究了它们及B位互掺杂的钙钛矿结构复合氧化物NdFe_xNi_1-xO₃的光催化活性。其光催化活性与Fe/Ni比有关。未掺杂的钙钛矿结构复合氧化物的光催化活性比B位互掺杂的钙钛矿结构复合氧化物NdFe_xNi_1-xO₃的光催化活性高。分别以固相法、溶胶-凝胶法和溶剂热法制备了银掺杂的钙钛矿结构复合氧化物La_（2-x）/3Ag_xTiO_3+λ,着重讨论了各合成方法和银的掺杂量对掺杂产物的颗粒形貌、粒径、表面相组成等参数的影响。研究表明,在La₂O₃-TiO₂体系中,掺杂Ag^（Ⅰ）对形成La_（2-x）/3Ag_xTiO_3+λ的钙钛矿结构起着至关重要的作用。其原因是Ag^（Ⅰ）可以使体系保持钙钛矿结构所必须的电荷平衡。因此,银的掺杂有利于La_（2-x）/3Ag_xTiO_3+λ的钙钛矿结构的形成。实验结果表明,在掺杂Ag^（Ⅰ）的情况下,较低反应温度和较短反应时间即可获得钙钛矿结构的复合氧化物La_（2-x）/3Ag_xTiO_3+λ。当银掺杂量（起始摩尔比）小于0.08时,产物中有未反应的起始物相存在;当银掺杂量大于0.1时,产物中明显有单质银存在,表明Ag^（Ⅰ）的掺杂量太低或太高,无法再通过缺陷或增加氧来调节电荷平衡,因此Ag^（Ⅰ）对形成钙钛矿晶体调节电荷平衡能力是有限的。研究了钙钛矿结构复合氧化物La_（2-x）/3Ag_xTiO_3+λ的紫外-可见漫反射吸收光谱,并利用Kubelka-Munk函数,计算了样品的半导体能隙,得出如下结果:Eg_{（Ag0.1-LT3）}>Eg_{（Ag0.1-LT2）}>Eg_{（Ag0.1-LT1）};Eg_{（Ag0.08-LT3）}>Eg_{（Ag0.06-LT2）}>Eg_{（Ag0.6-LT1）};Eg_{（Ag0.1-LT3）}>Eg_{（Ag0.08-LT3）}发现了在紫外光照射下钙钛矿结构复合氧化物La_（2-x）/3Ag_xTiO_3+λ的光致变色性质。探讨了La_（2-x）/3Ag_xTiO_3+λ的制备方法和银掺杂量与其光致变色性质的关系。研究结果表明,La_（2-x）/3Ag_xTiO_3+λ的光致变色性质主要与银的掺杂量有关。相同制备方法获得的样品,银掺杂量越多变色越快,颜色越深。探索了用钙钛矿结构复合氧化物La_（2-x）/3Ag_xTiO_3+λ作为修饰电极的循环伏安行为和电化学发光性质。结果表明,不同制备方法和不同掺杂量样品的修饰电极循环伏安曲线有明显差异,说明制备方法和掺杂量均对其表面银的含量和形态有明显影响。发现了La_（2-x）/3Ag_xTiO_3+λ修饰电极的电化学发光性质,其原因可能与其表面组成、银的形态、颗粒的形貌和粒径等因素有关,其电化学发光机理还有待进一步研究。采用溶剂热合成方法,以甘油和CTAB作为混合结构导向剂,合成了具有规则堆积孔道结构的TiO₂纳米晶,样品具有分散性好、粒径小和孔径分布窄等特征。样品HT2的粒径为5-10nm、孔径分布为4.2-6.2nm,比表面为285.3m²/g。实验结果表明,在晶体生长和焙烧过程中混合结构导向剂能有效地阻碍相邻晶核之间的团聚,控制品体的生长,可获得晶体粒径小且具有规则堆积孔道结构的TiO₂纳米晶。更多还原

【Abstract】 Perovskite-type oxides of ABO₃ have been extensively studied in recent years because of their unique physical and chemical properties. In this thesis, perovskite-type oxides of ABO₃ with different compositions and adjustable properties were taken as the subject and a series of ABO₃ and their doped composite oxides were successfully designed and synthesized by solid state reaction or soft-chemistry method. The obtained products showed good photocatalytic and photochromic properties. The influence of crystal structures, compositions and surface configuration of ABO₃ composite oxides on their photocatalytic activity was studied, and the electrochemiluminanscent property of electrode modified with silver-doped Perovskite-type composite oxides the was also explored. The thesis mainly focused on:Perovskite-type composite oxides of AFeO₃（A=Ce、Pr、Nd、Sm、Gd、Dy、Er、Y） and ANiO₃ （A=Nd、Gd） were successfully synthesized by the Stearic acid sol-gel method at a relatively low temperature （500℃-800℃）.The obtained products showed good crystallinity, high BET surface area and small average size. The photocatalytic property of ABO₃ and doped Nd_xFe_1-xNiO₃ composite oxides was evaluated, using photodecomposition of methylene blue as the model system and an XPA photochemical reaction meter. The results indicated that ABO₃ composite oxides have good photocatalytic activity and the inverse proportion of Fe/Ni has quite effect on its photoactivity in Nd_xFe_1-xNiO₃ composite oxides. In comparison with Nd_xFe_1-xNiO₃,NdFeO₃ showed better photocatalytic activity, and the decomposition rate of methylene blue was up to 99% within 90 min.The ceramic powder of perovskite type,La_1-xAg_xTiO_3+λ,has been synthesized by solid state reaction, sol-gel and solvothermal methods. The influence of synthetic methods and doping content of Ag on the size, surface composition and shape of the samples were investigated. It was found that the doping of Ag^（Ⅰ） played a key role in the formation of perovskite-type structure because Ag^（Ⅰ） was helpful to achieve the charge equilibrium for La₂O₃-TiO₂ system. Moreover, the doping of Ag^（Ⅰ） [x = 0.08-0.1 （molar ratio）] can lead to the formation of Ag-La_1-xAg_xTiO_3-λ with unique perovskite-type structure at lower temperature and shorter reaction time. However, small amounts of Ag was found to co-exist with La_1-xAg_xTiO_3-λ when the doping content of Ag^（Ⅰ） is more than 0.1, while reactants were found when the doping content of Ag^（Ⅰ） is less than 0.08. So the amount of doping Ag is limited. The UV-Vis spectra of the obtained Ag-La_1-xAg_xTiO_3+λ.powders were studied and the band gaps of each sample were estimated based on Kubelka-Munk Function. The results showed that Eg decreased in the sequences of Eg_{（Ag0.1-LT3）} > Eg_{（Ag0.1-LT2）} > Eg_{（Ag0.1-LT1）}Eg_{（Ag0.08-LT3）}> Eg_{（Ag0.06-LT2）} > Eg_{（Ag0.6-LT1）};Eg_{（Ag0.1-LT3）} > Eg_{（Ag0.08-LT3）}.It was found that Ag-La_1-xAg_xTiO_3+λ powders showed good photochromic property under ultraviolet light irradiation in air at room temperature. The effect of synthetic methods and doping content of Ag on the photochromic property of Ag-La_1-xAg_xTiO_3+λ powders was investigated. The results indicated that, for the samples prepared with the method, the more amount of Ag was doped, the deeper color of Ag-La_1-xAg_xTiO_3+λ was observed under UV radiation. The photochromic phenomenon of Ag-La_1-xAg_xTiO_3+λ is presumably due to the interconversion between Ag⁺ and Ag.The Cyclic voltamrnograms （CVs） behavior and electrochemiluminescent property of La_（2-x）/3Ag_xTiO_3+λ were explored, using La_（2-x）/3Ag_xTiO_3+λ modified glass carbon electrode. The data showed that La_（2-x）/3Ag_xTiO_3+λ obtained with different synthetic methods and different doping contents of Ag had different Cyclic voltammograms behaviour, indicating that the synthetic methods and doping contents of Ag have sonsiderable influence on the shape and content of Ag on the surface.La_（2-x）/3Ag_xTiO_3+λ modified glass carbon electrode also displayed electrochemi- luminescent property. This phenomenon may be caused by the substitution of Ag on the surface, particle size, surface composition and shape, etc. The electrochemi- luminescent mechanism of this system needs to be further investigated.The nanocrystalline titania with regular channel structure was synthesized, using a cetyltrimethylammonium bromide and nonsurfactant glycerol as a mixed structure-directing agent, by solvothermal method. Combination of the mixed structure-directing agent and solvothermal method resulted in the formation of nanocrystalline titania （HT2） with smaller size, higher crystallinity, better dispersibility, narrower particle distribution and much larger surface area. The experiment results showed that the average size of HT2 is 5-10 nm,the pore diameter is 4.2-6.2 nm and BET surface area is ca.285.3 m²·g^-1.Possible reason is that the combined structure-directing agents prevent the near crystals from congregating to each other effectively during the crystal growth and calcinations process, this is very helpful to obtain regular channel structure and small sized TiO₂ nanocrystals.更多还原