Study On The Preparation And Photocatalytic Activity Of N, S-doped NaTaO₃ And SrFeO₃

In the last decades, the semiconductor photocatalysis has attracted extensive attention due to its wide potential application in the treatment of all kinds of contaminants, especially for the removal of organic contaminants. However, most photocatalysts can only be excited by UV or near-UV radiation (only 5% of the natural solar light), which hinders its practical applications. So, it is of great significance to develop the photocatalysts that can be used in visible light, structural stability, easy recovery and reusable catalyst. Perovskites compounds with the diversity of structure and composition can be improved the photocatalytic activity by changing the composition, which is a promising kind of photocatalyst. But there are very few investigations about the perovskite photocatalysts. So, further strengthening the study on the systhesis and catalytic properties is of great significance for the development and improvement of photocatalytic technologyAmong these semiconductors, NaTaO3 with a perovskite structure show high activity for photocatalytic water splitting only under UV light irradiation, which hinders its practical applications. Due to this fact, NaTaO3 is not active under visible-light irradiation, which hinders its practical applications. To further improve the photocatalytic properties of NaTaO3, the effect of N, S elements doped on crystal structure, particle morphology, photocatalytic properties, and the doping mechanism were investigated. N-doped NaTaO3 (NaTaO3-xNx) was synthesized by the improved solid phase and one-step hydrothermal method, respectively. The results showed that the improved solid stated method requires low calcination temperature (only 700℃), which is obviously lower than 1000℃and avoidance of intermittent grinding. Although as prepared photocatalyst do not have visible light response, N doping can increased its photocatalytic activity under UV-light irradiation. The NaTaO3-xNx synthesized by hydrothermal method showed cubic morphology with the edge length of 200-500 nm. Moreover, this photocatalyst has good activity under visible light. All these results prove that the preparation method of photocatalyst is important for the photocatalytic activity increased.N elements doping can improve NaTaO3 photocatalytic activity, which may be related to the formation of O vacancies in crystal lattice after N doping. Researches indicate that in the case of the right nitrogen, the newly formed intra-band gap states can serve as a capture trap of photo-electron or cavity, which is conducive to photo-electron and cavity separation. The surface of photocatalyts can produce more OH·and·O2-, which can further promote separation of photo-electron and cavity. Moreover, the more strong oxidizing activity of radical, the higher photocatalytic activity.Perovskite SrFeO3 is a new material, but its photocatalytic activity is very few investigations. In this paper, SrFeO3 was prepared through two lines and its photocatalytic behavior was investigated in details. The experimental results showed that the addition of polyethylene glycol on the formation of pure phase SrFeO3 has a certain impact. When polyethylene glycol was not added, the final product contains SrCO3 impurities, which may be due to the samples reacted with CO2 in surrounding environment after cooling process. When polyethylene glycol was added, the pure phase SrFeO3 can be obtained. The possible reason is that during the sol-gel process, citric acid and ethylene glycol can form organic network which has excellent organic thermal stability and not prone to segregation during calcination, so the pure phase SrFeO3 can be prepared. The photodegradation results showed that compared with the pure phase SrFeO3, miscellaneous phase SrFeO3 has much higher photocatalytic activity, which may be due to the oxygen vacancies in the surface of pure phase SrFeO3 was much fewer than of impurity SeFeO3. Photocatalytic stability studies displayed that the lattice structure of impurity SrFeO3 collapsed and the pure phase SrFeO3 did not change after photocatalytic experiment, which indicate that SrFeO3 photocatalytic activity possibly come from Fe4+ ions in the lattice reacted with the surface oxygen vacancies.In summary, the effect of the nonmetallic element N, S doping on the crystal structure, morphology and photocatalytic properties and the stability of strontium ferrate during the degradation process were investigated. This study has important significance for the new semiconductor catalyst development, scientific research and practical applications.