Efficient sunlight-driven photocatalytic activity of chromium TiO₂ nanotube nanocomposites prepared by anodizing and chemical bath deposition

Different chromium-sensitized TiO₂ nanotube (CrTNs) nanocomposites were fabricated by anodizing of titanium in combination with a chemical bath deposition and pyrolysis process. The morphology and structure were characterized by field-emission scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. Optical properties were investigated by ultra UV–Vis diffuse reflectance spectra. The resulting CrTNs showed a tube diameter of 90–140 nm, wall thickness of 20–50 nm and tube lengths in the range of ~30 μm. The photocatalytic activity of the CrTNs was evaluated by measuring the degradation of methylene blue dye under simulated sunlight conditions and compared with photocatalytic activity of bare titanium dioxide nanotubes. The sample CrTN-3, that formed by anodizing of titanium in ethylene glycol electrolyte and then soaked in a H₂O/ethanol (4:1) solution containing 0.05 M CrCl₃·6H₂O for 3 h at 70 °C, exhibited better photocatalytic activity than other CrTNs samples. The process developed in this study is facile, reproducible, and inexpensive, and can be easily scaled up, thereby pioneering the fabrication of high performance photocatalysts with promising environmental applications.