Effective Photocatalytic Performance of Ordered Mesoporous Fe₂O₃–TiO₂ Under Visible Light

Ordered mesoporous Fe₂O₃, TiO₂, and Fe₂O₃–TiO₂ composites with different molar Ti to Fe ratio were prepared via a nano-replication method using highly ordered mesoporous silica as a hard template. Physicochemical properties of the mesoporous catalysts were characterized by X-ray diffraction, electron microscopy with energy-dispersive X-ray spectroscopy, and N₂ adsorption–desorption analysis. The photocatalytic performances of the catalysts were evaluated in terms of methylene blue removal efficiency, using 70 ppm methylene blue solution with 5 mM H₂O₂ as an assistive oxidant under UV light and visible light generated by 150 W xenon lamp system. Rate constant values were used to compare photocatalytic activities of the prepared samples. Under UV light, ordered mesoporous TiO₂ showed the highest rate constant as expected, and ordered mesoporous Fe₂O₃–TiO₂ (1:1) and (1:2) exhibited comparable catalytic activities to TiO₂. In the case of visible light irradiation experiment, the highest rate constant was observed over the catalyst with Fe:Ti molar ratio of 1:1, which is probably due to its low band gap energy (about 1.90 eV). The excellent photocatalytic activity of ordered mesoporous Fe₂O₃–TiO₂ (1:1) under both UV and visible light irradiation can be explained as a consequence of the large surface area with large pore volumes, and charge separation ability enhancement by heterojunctions between Fe₂O₃ and TiO₂.