Effects specific surface area and oxygen vacancy on the photocatalytic properties of mesoporous F doped SnO₂ nanoparticles prepared by hydrothermal method

Mesoporous Fluorine doped SnO₂ (FTO) nanoparticles (NPs) have been successfully synthesized by hydrothermal process. Subsequent annealing process at 350 °C, 500 °C, 650 °C and 800 °C has been carried out to synthesize FTO photocatalysts with different specific surface areas and oxygen vacancy contents. X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy characterization, Raman measurement, X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflectance and Photoluminescence (PL) spectra have been used to investigate the effects of specific surface areas and oxygen vacancy contents on the photocatalytic properties of mesoporous FTO photocatalysts. The results show that the mesoporous FTO NPs consist of spherical nanoparticles of 3–6 nm in diameters with a tetragonal crystal structure. The as–synthesized mesoporous FTO NPs with the band gap of 3.91 eV, the largest number of oxygen vacancies and the largest surface area of 145.55 m² g⁻¹ exhibit an excellent photocatalytic activity when degrading methyl orange (MO) under UV light irradiation, and the degradation of dye methyl orange (MO) can reach 97% within 80 min. Moreover, the superoxide oxide (•O₂⁻) is the major active specie, which has played a key role in MO degradation system. The photocatalytic mechanism of FTO photocatalysts has been also proposed.