The Controlled Preparation Of ZnGa₂O₄ Nanocrystals And Its Photocatalytic For Water Splitting Into Hydrogen

In photocatalysis field, efficient photocatalysts have been aroused public attention in recent years. Nanometer materials attracted widespread attention because of its high surface-volume, quantum-size effect and small-size effect. Many researchers combined the semiconductor photocatalysts with nanometer materials, then treated by some methods to improve their activity. Currently, most photocatalysts with d0 electronic structure, however, semiconductor materials with d10 electronic structure had high electron mobility, could exhibit excellent performance in photocatalysis field. In this paper, we chose ZnGa2O4 with d10 electronic structure as main base material, in order to improve the activity of the ZnGa2O4 materials. Firstly, sodium citrate was added as a surfactant and complexing agent to control ZnGa2O4 morphology, then, this material’s surface treated with some inorganic acid to improve the activity; Secondly, we synthesized novel structure—core\shell structure by stage heating under hydrothermal conditions. The main research are showed as follows:In the second chapter, we added sodium citrate to control the morphology of ZnGa2O4 material, TEM results showed adding sodium citrate could make irregularly dispersed ZnGa2O4 nanoparticles form orderly ZnGa2O4 nanospheres. Though the sodium citrate played the key role in the formation of the ZnGa2O4 nanospheres, it seriously restricted the photocatalytic performance. We found that the samples treated by inorganic acid and exhibited the excellent performance, which the amount of hydrogen production is three times more than the calcined samples’. TEM, SEM and XRD results showed that the morphology and size of ZnGa2O4 nanospheres unchanged, X-ray photoelectron spectroscopy (XPS) and UV-Vis were combined to investigate the reason of high photocatalytic activity. The position of the bottom of the conduct band move up, that is to say, the reduction ability of conduct band improved. Besides, the results of photocurrent measures and AC Impedance tests showed that the high separation and transfer efficiency of photogenerated electron-hole pairs, which is the other reason of good performance.In the third chapter, we successfully synthesized the core\shell nanospheres with the ZnGa2O4 nanospheres as the hard-template, made the ZnGa2O4 nanoparticles loaded uniformly on the ZnGa2O4 nanospheres by stage heating under hydrothermal conditions, and formed the resulted structure through Ostwald Ripening process. We studied the influence of temperature and the amount of the hard-template on the structure of synthesis. The results of UV-Vis showed that the core\shell nanospheres had higher photo-absorption efficiency because of its inner space, than the ZnGa2O4 nanospheres. We concluded that the formation of the core\shell nanospheres can improve the photocatalytic activity.