Synthesis of TiO₂ Nanotubes and Its Photocatalytic Activity for H₂ Evolution

TiO₂-derived nanotubes were prepared by hydrothermal treatment in 10 M NaOH(aq) by using commercially available TiO₂ (Degussa P-25) as starting material. N₂-adsorption/desorption analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) observations of the obtained product revealed the formation of titanate nanotube structure with its diameter of about 10–20 nm. The effect of post-heat-treatment on the phase structure, morphology, specific surface area and photocatalytic activity was investigated. The TiO₂ (B) nanotubes could be observed at post-heat-treatment of 300 °C. As post-heat-treatment was increased to 400 °C, the nanotubes began to transform into nanoparticles of anatase phase, producing a bi-crystalline mixture of TiO₂ (B) nanotubes and anatase nanoparticles. Moreover, the particles changed into rutile phase through the post-heat-treatment at higher temperatures over 700 °C. The photocatalytic activity of prepared samples was evaluated with photocatalytic H₂ evolution. The results showed that the TiO₂-derived nanotubes treated at appropriate temperature exhibited high H₂ evolution.