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 °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 (~ 550 nm) compared to the pristine TNTs (~ 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. Graphic abstract: [Figure not available: see fulltext.].