Synthesis of Graphite Doped TiO2 Nanotubes, and Their Structural, Electronic, and Photocatalytic Characterization

Self-organized and vertically oriented TiO2 nanotubes (TNTs) were synthesized via anodization of Ti sheet in a glycerol-based used electrolyte. Graphite (Gt) is doped in TNTs by physical vapor deposition (PVD) under Ar-atmosphere at 700 degrees C using polyvinyl alcohol (PVA) as a precursor. The samples were characterized using FESEM, HRTEM, XRD, Raman, XPS, and UV-vis diffuse reflectance spectroscopy. HRTEM, XRD, and Raman analysis confirm the suppression of phase transformation from anatase to rutile due to Gt doping. The UV-vis absorption properties and photocatalytic activity of the pristine and Gt-doped TNTs have been investigated. The bandgap absorption edge of Gt-doped TNTs shifts towards a higher wavelength (similar to 550 nm) compared to the pristine TNTs (similar to 390 nm). Moreover, the Gt-doped TNTs show strong absorption in the visible region. This makes it a good candidate for energy-storing applications. It has been found that Gt-doped TNTs display two-fold enhanced photocatalytic activity for methyl orange (MO) degradation compared to pristine. The enhanced photo-degradation of Gt-doped TNTs is ascribed to the higher absorptivity, better crystallinity, and lower bandgap of TNTs due to Gt doping. The enhanced photo-degradation ability of Gt-doped TNTs can be used to clean industrial wastewater.