Synthese And Property Studies Of Metal Sulfide And Oxide Hollow Structures

Hollow micro-and nano-structures have attracted great interest because of their unique properties and promising applications in many areas, and become a popular research subject in materials chemistry and science. Up to date, a common synthetic strategy for the fabrication of hollow structures employs template approach. However, templating methods for preparation of hollow structures are usually time-consuming and costly. Therefore, it is highly desirable for basic researches and technology applications to develop facile approaches for the preparation of hollow spheres, and further tune their chemical and physical properties.In this thesis, a series of metal sulfide and oxide hollow structures have been synthesized through simple approaches, such as Ostwald process and Kirkendall effect. The formation mechanism of hollow materials and the relationship between property and morphology were discussed. The main contents of this thesis are summarized as follows:1. Synthesis of CdS hollow spheres through Ostwald process and their photocatalytic property studies:CdS hollow spheres were prepared with the assistance of biopolymer soulcarboxymthyi chitosan via Ostwald process. By adjusting the reaction conditions, CdS nanomaterials with different structures were successfully obtained. The photodegradation of methyl orange (MO) with different CdS as catalysts was studied. The experimental results demonstrated that the CdS hollow spheres exhibit the best photocatalytic abilities.2. Synthesis of multilevel Bi2S3 superstructures assembled by Bi2S3 nanorods: BiOCOOH hollow structures assembled by nanosheets were prepared by a quasimicroemulsion approach. Flower-like BiOCOOH was also prepared by changing the reaction conditions. The photocatalytic degradation of RhB with BiOCOOH as photocatalysts was studied, which demonstrates that the hollow BiOCOOH spheres exhibit better photocatalytic activity. BiOCOOH structures can be transformed to Bi2S3 and Bi2S3 superstructures assembled by 2D networks were successfully obtained through ion exchange reaction. The close lattice matching between the tetragonal BiOCOOH and orthorhombic Bi2S3 could be responsible for the formation of superstructures Bi2S3 hollow spheres and flower-like Bi2S3 assembled by 2D Bi2S3 network.3. Synthesis and their transformation of polycrystalline a-NiS hollow sphere and single-crystalline β-NiS hollow spheres:Uniform polycrystalline a-NiS hollow spheres were prepared through Kirkendall effect under hydrothermal conditions with thiourea and glutathione as sulfur source. By simply raising the reaction temperature, polycrystalline a-NiS hollow spheres can be transfered to single-crystalline β-NiS hollow spheres. The adsorption capacities of NiS with different morphologies were studied, which reveals that the hollow NiS spheres exhibit excellent abilities to remove organic pollutant Congo red from water.4. Synthesis of ZnS hollow spheres through Ostwald process and their antibacterial properties:ZnS hollow spheres were successfully prepared via Ostwald process in glycerol and water mixed solution. By varying the reaction conditions, ZnS solid spheres and nanoparticles were successfully obtained. The antibacterial activities of ZnS with different morphologies were studied, which demonstrated that the structures of ZnS materials have great effects on the antibacterial activity.5. Synthesis of CeO2 and CeO2/MnOx core-shell structures:Hollow precursor spheres have been prepared with the assistance of tartaric acid via solvothermal approach. The core-shell CeO2 was obtained by annealing the precursor hollow spheres. The difference diffusion rates between the surface and inner of hollow spheres was responsible for the formation of core-shell CeO2. Meanwhile, this approach was developed to prepare CeO2/MnOx composite materials.6. Synthesis of graphene-like 2D MnO2 nanosheets:Through simple redox reaction between KMnO4 and carbon spheres, C@MnO2 core-shell structures were firstly obtained. Ultrathin 2D MnO2 nanosheets were finally obtained by further increasing the reaction time. The ultrathin 2D MnO2 nanosheets exhibit great electrochemical performances as electrode material for Li-ion battery. The first discharge capacity is about 906 mAh·g-1 at a current density of 200 mA·g-1, and the discharge capacity is about 732 mAh·g-1 after 100 cycles. Furthermore, ultrathin MnO2 nanosheets present high catalytic activities towards CO oxidation.