Controllable Preparation And Property Investigation Of Nano-sized Tantalates Photocatalysts

Controllable synthesis of nanoparticles is one of the most important sections of nanoscience and nanotechnology, and also the base to investigate the distinctive properties and applications of nanostructures. The main points of this thesis rest with exploring novel hydrothermal methods to synthesize functional composite oxides nanomaterials,and exploring the photocatalytic property of the products and investigating the relationship between the morphology and photocatalytic property.In the aspect of investigating dimension and shape manipulated synthesis of low-dimensional functional nanomaterials, results on selective synthesis of tantalates nanosheets and nanorods. Layered Ba5Ta4O15 nanosheets had been firstly synthesized through the designed hydrothermal process. The thickness of nanosheet was about 1.1 nm, which corresponded to a monolayer of Ba5Ta4O15 molecules, with the lateral size ranging from 50 to 200 nm. The dissolution–recrystallization mechanism was suggested based on observations of the factors that influence nanosheet formation, such as reaction time, temperature, and basicity. Formation of Ba5Ta4O15 nanosheets took precedence over other nanostructures under high concentrations of OH- because the hindering effect of OH- ions on the c-axis growth is strong. The Ba5Ta4O15 nanosheets showed a high photocatalytic activity. The layered perovskite probably affected the photocatalytic activity by promoting the charge separation and delocalization of photogenerated electrons and holes.BaTa2O6 nanorods were synthesized via a hydrothermal method based on adjusting the concentration of reactants. The formation of BaTa2O6 nanorods was depended on the chemical potential of crystal planes. Hydrogen-related defects were detected in BaTa2O6 nanorods, which originated from the oxygen octahedron. The number of defects was dependent on the hydrothermal temperature, and the photocatalytic activities of BaTa2O6 nanorods increase with the decrease of defect amounts. On the basis of the experiment results, the difference in photocatalytic activities for samples is mainly caused by lattice defects, which can act as inactivation centers.The surface properties and physiochemical was modified by non-metal elements doping in the tantalates photocatalysts. The N-doping tantalates exhibited photocatalytic performance under visible-light, and the photocatalytic activity can be improved after being modified by fluorine ion. Investigations on the photocatalytic reaction between tantalates and TiO2 were made to elucidate the possible photooxidation mechanism. The photocatalytic degradation of organic pollutants in tantalates was mainly direct holes oxidation.