Fabrication and photocatalytic activity of TiO2/SiO2 composite nanotubes

TiO2/SiO2 composite nanotube photocatalysts supported on Al substrates were prepared by the anodic aluminum oxide (AAO) liquid-phase deposition method for degradation of 100 mg/L methyl blue (MB). AAO templates were prepared in H3PO4 acidic electrolytes through the two-step anodic oxidation method. The photocatalysts were characterized by field-emission scanning electron microscopy, thermal analysis (TG-DTA), and Fourier-transform infrared, x-ray photoelectron, and UV–Vis diffuse spectroscopies. The results showed that the presence of SiO2 in TiO2 inhibited the crystal phase transformation temperature effectively, with a greater wall thickness of 80–100 nm. It was found that Ti–O–Si bonds were formed on the surface and the surface hydroxyl concentration was increased, resulting in enhanced photocatalytic activity, being about 20% higher than for pure TiO2 films. The calculated band structure for TiO2/SiO2 was investigated using first-principle calculations. The TiO2/SiO2 composite exhibited a wider conduction band which would effectively prohibit recombination of photogenerated electrons and holes.