Abstract
In this report, the photocatalytic activity of P25 has been explored and the influence of thermal treatment under various atmospheres (air, vacuum and hydrogen) were discussed. The samples’ characteristics were disclosed by means of various instruments including X-ray diffraction (XRD), Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and UV–vis. This study also accentuates various states of the oxygen vacancy density formed inside the samples as well as the colour turning observed in treated P25 under various atmospheres. Produced coloured TiO2 samples were then exploited for their photocatalytic capability concerning photodegradation of methylene blue (MB) using air mass (AM) 1.5 G solar light irradiation. Our findings revealed that exceptional photocatalytic activity of P25 is related to the thermal treatment. Neither oxygen vacancy formation nor photocatalytic activity enhancement was observed in the air-treated sample. H2-treated samples have shown better photoactivity which even could be further improved by optimizing treatment conditions to achieve the advantages of the positive role of oxygen vacancy (O-vacancy at higher concentration than optimum acts as electron trapping sites). The chemical structure and stability of the samples were also studied. There was no sign of deteriorating of O2-vacancies inside the samples after 6 months. High stability of thermal treated samples in terms of both long and short-term time intervals is another significant feature of the produced photocatalyst.
Highlights
The intermediate conducting ability of titanium dioxide (TiO2) has converted it to an oxide semiconductor which holds an especial place in environmental applications that require a photoactive material; TiO2 only functions with the aid of UV light due to its large energy band gap [1,2,3]
Obvious signals at g equals to 2.001 in the Electron paramagnetic resonance (EPR) spectra of H-400 and V-400 might be ascribed to oxygen vacancy generation in these samples [52,53]
Generation of oxygen vacancy in P25 samples by thermal treatment under vacuum and hydrogen atmospheres at different temperatures (200, 300, 400 and 500 °C) was successful
Summary
The intermediate conducting ability of titanium dioxide (TiO2) has converted it to an oxide semiconductor which holds an especial place in environmental applications that require a photoactive material; TiO2 only functions with the aid of UV light due to its large energy band gap [1,2,3]. Since pure TiO2 cannot absorb the wavelengths greater than 387 nm and solar irradiation’s wavelength lies beyond that margin, solar visible light cannot be applicable. Majority of studies with respect to band gap engineering are focused to improve TiO2 photocatalytic performance. In this respect, one way is to decorate the TiO2 surface by dopants, such as metals and non-metals. One way is to decorate the TiO2 surface by dopants, such as metals and non-metals Cations such as Mn, Ag, Au, Cr, La and Fe were utilized as metal dopants and they could decrease TiO2 bandgap when are completely dispersed into its lattice [4,5,6]. Non-metal dopants such as N [7,8,9,10], C [11,12,13] and
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