Impact of Cr Doping on the Optical, and Photocatalytic Performances of TiO2 for Solar Drivin Wastewater Treatments

Abstract Commercially used chemical pollutants, such as methylene blue (MB) dye, are dumped into water reservoirs and can potentially harm both humans and aquatic life. To investigate the effect of Cr doping on the morphological, structural, optical, and photocatalytic properties of TiO₂, Cr-doped TiO₂ nano photocatalysts were synthesized using a simple and cost-effective single-step sol-gel technique. XRD investigations revealed that all of the samples contain only the anatase phase, and the absence of any extra Cr peaks indicates successful Cr doping. Furthermore, Cr doping causes a considerable increase in the average crystallite size of TiO₂ nanocrystal from 71.42 to 86.16 nm. The Fourier Transform Infrared (FTIR) spectra revealed the presence of functional groups (Ti-O and H-O) in all of the samples. UV absorbance spectra tauc plots showed that Cr doping caused the TiO₂ band gap to shrink from 3.21 eV to 2.90 eV. In addition, the generated Cr-doped TiO₂ nano photocatalysts were used to degrade MB dye under direct sunlight irradiation photocatalytically. At optimal conditions, the photo-degradation efficiency of MB dye achieved 21.24%, 31.18%, and 35.76%, for pure, 0.3%, and 0.5% Cr-doped TiO₂ respectively. A high rate constant of 2.24 x 10⁻ ³ min⁻ ¹ was observed for 0.5% Cr-doped TiO₂ nano photocatalyst. An increased photocatalytic activity of Cr-doped TiO₂ in visible light makes them ideal candidates for solar-powered water filtration systems.