新型纳米铁电钛酸钡的尺寸效应对其光催化性能影响及构-效关系研究

Ferroelectric materials are considered as a promising candidate for photocatalysts due to its built-in electric field, which can assist charge carriers separation and inhibit its recombination. However, the size effect of ferroelectric materials and the associated changes in its ferroelectricity are inevitable when we design high-efficiency nanoscale ferroelectric photocatalysts. This project chooses ferroelectric barium titanate as the research target and intends to prepare a series of barium titanate powder with various particles sizes through microwave-assisted solventhermal method, followed by surface decoration with dual co-catalysts by using photodeposition method. Then the photocatalytic properties of these photocatalysts will be assessed by photodegradation of organic pollutants under solar irradiation. The varieties in crystalline structure and tetragonality arising from size effect will be analyzed, and the spontaneous polarization of different-size barium titanate will be calculated. Combing these varieties in ferroelectricity with its photodegradation efficiency and lifetime of charge carriers, the relationship between the ferroelectric structure and photocatalytic properties will be elucidated, and the mechanism how the built-in electric field in ferroelectrics influences the kinetics of charge carriers will be discussed. This project aims to uncover the influence of size effect in ferroelectrics on its photocatalytic performance, determine the optimum particle size of ferroelectric baritum titante as photocatalysts, and provide a clue for designing nanoscale ferroelecric photocatalysts.

铁电材料因其内部自发极化场能够驱动光生电荷的有效分离，抑制载流子复合，提高光催化效率，正成为一种极具潜力的新型光催化剂。然而铁电材料的尺寸效应所引发的铁电相结构与铁电性能的变化是纳米铁电光催化材料设计与应用过程中不可忽视的因素。本项目以铁电钛酸钡为研究对象，通过微波溶剂热法制备一系列不同粒径的高纯四方相钛酸钡粉体，并采用光沉积法对钛酸钡粉体进行双助催化剂的表面修饰，研究其在太阳光下降解有机污染物的光催化性能；分析钛酸钡的尺寸效应引起的晶体结构和四方度等铁电相结构的变化，计算不同粒径下钛酸钡的自发极化强度，结合其相应的光降解染料的反应速率与载流子寿命的变化，探索铁电钛酸钡的内建电场对载流子运动的影响机理，构筑铁电相结构与光催化性能的构-效关系。本项目旨在揭示铁电钛酸钡的尺寸效应对其光催化性能的影响规律，探讨铁电钛酸钡在光催化领域应用的最佳粒径，进而为新型纳米铁电光催化剂的设计奠定基础。

铁电材料因其内部自发极化场被证明能够驱动光生载流子的有效分离，提高光催化效率，被认为一种新型的极具潜力的光催化剂。然而铁电材料的铁电相结构与其光催化效率之间的构效关系尚不明确，尤其是铁电材料的尺寸效应引发的铁电性的变化是纳米铁电光催化剂的设计过程中不可忽视的因素。.本项目选取经典的钛酸钡为研究对象，首先采用水热法成功制备了粒度均一的纳米铁电钛酸钡粉体；采用一步光沉积法在钛酸钡的表面同时负载还原助催化剂Ag和氧化助催化剂MnOx，构筑了双助催化剂协同修饰钛酸钡Ag/BTO/MnOx；采用太阳光下降解罗丹明B染料对获得的光催化剂进行了光催化活性表征，同时对光生载流子的运动、染料降解的中间产物和光催化反应机理进行了系统研究，结果表明Ag/BTO/MnOx的光降解反应速率是Ag/BTO的3倍，是BTO/MnOx的12倍，双助催化剂的优越性归因于促进光生载流子的分离；同时通过对降解中间产物和降解路径的分析，表明染料分子在Ag/BTO/MnOx与Ag/BTO体系的降解路径不同，这是由于还原助催化剂的MnOx的存在，改变了染料分子在催化剂表面的吸附模式；对获得的具有不同粒径和铁电相结构的钛酸钡粉体，分析其铁电相结构的变化，并基于四方铁电钛酸钡BTO-A（~250 nm）和立方非铁电钛酸钡BTO（~600 nm），分别构筑钛酸钡/三氧化二铁复合光催化剂，并对比分析两种复合光催化剂的光催化性能，结果表明以BTO-A为基体的复合光催化剂其降解速率是以BTO为基体的1.5倍，构建了铁电内建电场在铁电材料-半导体异质界面的作用模型，证明BTO-A为基体的复合光催化剂的优越性在于其内部偶极子能够有效驱动与其复合的半导体内部光生电荷的分离，阐明了铁电相结构与光催化性能的构-效关系。本项目的执行有助于加深对新型纳米铁电光催化剂内建电场与光生载流子运动行为关系的理解，对新型纳米铁电光催化剂的设计奠定一定基础。