Microstructure and photocatalytic activity of porous TiO2–Fe2O3 composite film by PEO coupled with post heat treatment

Porous composite TiO2–Fe2O3 film was fabricated on steel by plasma electrolytic oxidation (PEO) coupled with post heat treatment. The microstructure of the film including phase composition, element constituent, surface and cross sectional morphologies and photocatalytic activities of the films were investigated. The results revealed that film obtained by PEO coupled with post heat treatment was composed of crystal TiO2, Fe2O3, and some Al2O3 was also presented in the film. The film showed porous surface, and large pores was about 1–2 μm and that many small holes were in the range 300–500 nm. There were many ball-shaped and plate-shape TiO2 particles on the surface. Many of the ball-shaped particles were in dimension of nano scales and some larges are around 1 μm. The thickness was about 18 um. The optical adsorption properties of the film was investigated by UV–vis diffuse reflectance spectra which showed that the film exhibited strong adsorption in visible with the band gap of about 2.89 eV. The photocatalytic activity of the film was evaluated through the degradation of methylene blue. The film exhibited desirable photocatalytic activity with the degradation ratio of 82% methylene blue under 240 min irradiation of visible light.