Strontium and manganese co-doped TiO2 nanoparticles for the enhanced photocatalytic degradation of methylene blue dye

In this study, manganese-doped titanium dioxide nanoparticles (Mn–TiO₂), strontium-doped titanium dioxide (Sr–TiO₂), and co-doped with both manganese and strontium (Mn–Sr–TiO₂) were synthesized using the sol–gel method. The resulting powders underwent comprehensive characterization employing techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Diffuse Reflectance Spectroscopy (UV–DRS), and Fourier-transform infrared spectroscopy (FT–IR). X-ray diffraction pattern analysis confirmed the presence of the anatase phase in the catalyst. According to the Scherrer equation, the crystallite size was estimated to be 12 nm for pure TiO₂ and 10 nm for co-doped TiO₂. Importantly, co-doping induced a reduction in the band gap energy, decreasing from 3.3 to 3.05 eV. The photocatalytic performance of the synthesized materials was evaluated for the degradation of methylene blue (MB), revealing that co-doping facilitated the degradation of 95% of the target compound (MB) within 2 h. The synergistic interaction of manganese and strontium ions played a crucial role in reducing the band gap of TiO₂ and delaying the recombination of photo-generated electrons and holes. This synergistic interplay between manganese and strontium enhanced photocatalysis, reducing the total organic carbon (TOC) content from 35.6 to 5.5 mg/l after 2 h of UV light exposure.

Graphical Abstract