Abstract
TiO2 (Degussa P25) photocatalysts harboring an abundant oxygen vacancies (vacuum P25) were manufactured using a simple and economic vacuum deoxidation process. Control experiments showed that temperature and time of vacuum deoxidation had a significant effect on vacuum P25 photocatalytic activity. After 240 min of visible light illumination, the optimal vacuum P25 photocatalysts (vacuum deoxidation treated at 330°C for 3h) reaches as high as 94% and 88% of photodegradation efficiency for Rhodamine B (RhB) and tetracycline respectively, which are around 4.5 and 4.9 times as that of pristine P25. The XPS, PL and EPR analyses indicated that the oxygen vacancies were produced in the vacuum P25 during the vacuum deoxidation process. The oxygen vacancies states can produce vacancy energy level located below the conduction band minimum, which resulting in the band gap narrowing, thus extending the photoresponse wavelength range of vacuum P25. The positron annihilation analysis indicated that the concentrations ratio of bulk and surface oxygen vacancies could be adjusted by changing the vacuum deoxidation temperature and time. Decreasing the ratio of bulk and surface oxygen vacancies was shown to improve photo-generated electron-hole pairs separation efficiency, which leads to an obvious enhancement of the visible photocatalytic activities of vacuum P25.
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