Hydrothermal Synthesis And Electronic Structure Study Of V/W Doped Nano-NaTaO₃

Nano-NaTaO3 of perovskite structure is a new photocatalysis, which has a great potential application in dissolving the energy insufficiency and environmental pollution nowadays. However, NaTaO3 is a wide band gap semiconductor with band gap of 4.0 eV and its application is significantly restricted because of its failure to use the green energy source of sunlight. In this thesis, a series of V or W doped NaTaO3 nanostructure were synthesized via the hydrothermal route. By systematic characterization using XRD, SEM, UV-vis-DRS, and FI-TR, phase structure, morphology, vibration property, and absorption properties of samples were studied in detail. Density functional theory was used to process a simulated calculation on the changes of band structure, DOS,PDOS, and to explain the mechanism of band structure modification and formation on NaTaO3 via V and W doping. The following results were achieved:1. XRD patterns of V doped NaTaO3 prepared by hydrothermal method illustrated that the diffraction peaks systematically shifted to lower angle, suggesting vanadium is introduced to NaTaO3 in two ways:V5+ replaced Ta5+ via ion exchange or V anchored into the lattice of NaTaO3. Universal cubic morphology were observed by SEM. UV-Vis-DRS spectra of samples showed the obvious red-shift of absorption peaks with increasing of V doping content, indicating the narrowed band gap.2. Density functional theory was applied to conduct simulated calculation of band gap structure and DOS. The results indicated that V doping could form an incorporation energy levels with 3 d orbital of vanadium, which mainly attributed to lower the energy needed in the electron jump, therein, extended the light absorption of NaTaO3.3. W doped NaTaO3 samples were prepared via hydrothermal method. The diffraction peaks of The XRD patterns of showed no shift with W doping, while no obvious changes were observed from the UV-Vis-DRS. The results of DFT calculation show that band position of NaTaO3 shift down after W doping and W 5d locate above the Ta 5d level. There were no changes at the bottom of conduction band and the top of valance band with W doping into NaTaO3.4. With instruction of computational chemistry related theory and methods, computational molecular material designing platform were constructed by using structural mode of Client/Server. And quantum chemistry software NWChem and molecular dynamic software CPMD were successfully introduced to the platform. Further, we construdcted tow different softeware applications, which is believed to be usfull to the future research.