Photocatalytic degradation of Orange G using TiO2/Fe3O4 nanocomposites

Titanium dioxide (TiO2) is one among the best photocatalysts used in commercial applications. However, its large intrinsic bandgap (similar to 3.23 eV) limits its photocatalytic application only to the ultraviolet (UV) region that is only 4% of the solar spectrum. The recombination of photogenerated electron-hole pairs reduces the quantum efficiency and photocatalytic activity. The visible region allows us to use 43% of the solar spectrum. Therefore, to extend the photocatalytic activity of TiO2 to visible light spectrum, its bandgap must be decreased that suppresses the recombination reactions. This can be achieved by coupling of semiconductor metal oxides having different bandgap values with TiO2 for the efficient use in the visible light region. In this work, magnetite (Fe3O4) nanoparticles were synthesized by a modified co-precipitation method, and it was used to prepare a TiO2/Fe3O4 nanocomposite with three different ratios (0.2/0.8, 0.5/0.5, and 0.8/0.2). The obtained nanocomposite was characterized using X-ray diffraction, Raman and ultraviolet-visible spectroscopies, and scanning electron microscopy fitted with scanning transmission electron microscopy to understand the various properties such as crystallinity, optical properties, and morphology of the nanocomposites. We noticed that the crystallite size of TiO2 in the nanocomposite, as well as the bandgap energy of the nanocomposite, decreases with the increasing Fe3O4 content. The degradation of Orange G with Fe3O4, TiO2, and nanocomposites with three different ratios was studied in a solar simulator under different exposure times. Our studies show that (TiO2)(0.2)(Fe3O4)(0.8) nanocomposite having small crystallite size and bandgap gives the best photocatalytic activity under visible light among other ratios.