Preparation and characterisation of bismuth-doped TiO₂ nanotubes (Bi-TiO₂-NT) and its photocatalytic activity test for rhodamine B elimination under visible light

As a photocatalyst, TiO₂ nanotubes can effectively degrade dyes; thus, they exhibit a considerable potential to mitigate the problem of river pollution by dye waste originating from the textile industry. However, with a band gap of 3.2 eV (UV light energy range), such nanotubes cannot be completely utilizing under visible light from the sun. Therefore, in this study, the TiO₂ nanotubes are modified using bismuth to obtain bismuth-doped TiO₂-NT (Bi-TiO₂-NT), which exhibits an activity under visible light. Bi-TiO2-NT was successfully synthesized by one-step anodization with Bi(NO₃)₃ as the dopant source. The optimum synthesis conditions obtained were as follows: 1.0 M Bi(NO₃)₃ in an ethylene glycol electrolyte with anodization at 40 V for 1 h. In this study, the synthesized photocatalyst was characterized using X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), UV-Vis Diffuse Reflectance Spectroscopy (DRS), Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS), and Linear Sweep Voltametry (LSV). The results of the photocatalytic activity tests indicated that under visible light illumination the prepared Bi-TiO₂-NT was able to eliminate rhodamine B from the tested water, better then bare TiO₂.