Photocatalytic activity of Fe and Cu co-doped TiO2 nanoparticles under visible light

The photocatalytic activity of single transition metal-doped TiO2 nanoparticles is well established. This article reports the synthesis of Fe and Cu co-doped TiO2 nanoparticles with varying Fe and Cu concentrations by the sol–gel method and their photocatalytic activity towards photodegradation of methylene blue under visible light. Nanoparticles were characterized by X-ray diffractometry (XRD), Raman spectroscopy, Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence spectroscopy (XRF), and Diffuse reflectance UV–Visible spectroscopy. XRD patterns revealed the existence of both anatase and rutile phases which was confirmed by Raman and TEM analysis. Both XRD and Raman analysis confirmed the successful doping of Fe and Cu without causing any significant lattice distortions. Nanoparticles were aggregated as shown in TEM and SEM images. XPS analysis revealed the presence of the only Ti4+ in pure TiO2 while both Ti4+ and Ti3+ were present in doped TiO2 in addition to Fe3+, Cu+, and Cu2+. XRF analysis showed the presence of only Ti, Fe, and Cu in the co-doped nanoparticles. According to the diffuse reflectance spectroscopic analysis, the visible light sensitivity of TiO2 has increased upon doping with Fe and Cu. Single metal-doped nanoparticles were efficient than the co-doped nanoparticles for the degradation of methylene blue under visible light. Among the single doped nanoparticles, 0.05 Cu/TiO2 showed the highest rate constant (0.0195 min−1) while the maximum activity from the co-doped nanoparticles resulted in 0.05 Cu + 0.05 Fe/TiO2 (0.0098 min−1). The photocatalytic activity was decreased upon increasing the dopant (Fe/Cu) concentration due to the recombination of photogenerated electron-hole pairs, while due to the shielding effect, low photocatalytic activity resulted in co-doped nanoparticles with varying Fe and Cu loadings.