Surface modification of TiO2 with a less expensive metal (iron) to exploit solar energy in photocatalysis: An ecological and economical solution

Abstract To degrade the tryptophan molecule through photocatalysis, the exploitation of solar energy in the present study necessitated the use of visible light active photocatalysts. Iron-transition metal nanoparticles were deposited on the surface of TiO2 powders through an impregnation method to obtain X%Fe-TiO2 for the purpose of improving the optical absorption of TiO2 in the visible light region. The effects of iron percentage (X%: 2,4 and 5), iron oxidation state and pH on the photocatalytic performance of TiO2 modified under solar irradiation were thoroughly studied. The characterization results by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS) and scanning electron microscopy/energy dispersive X-ray spectrometry (SEM-EDS) indicate that iron nanoparticles were successfully fixed on the TiO2 surface. The absorption wavelengths of all X%Fe-TiO2 photocatalysts shifted towards the visible, confirming successful modification of the TiO2 surface with iron. Based on the empirical results, X%Fe-TiO2 nanomaterials demonstrate a higher activity compared with the unmodified TiO2 under solar irradiation. The 4%Fe(III)-TiO2 photocatalyst, in particular, displayed the highest photocatalytic activity at natural pH. The degradation was complete in 60 min. Therefore, it is interesting to note that iron had more functions and benefits than noble metals. The mechanism of the Fe-TiO2 system has been proposed in detail.