Enhancement in hydrogen generation using bamboo like TiO2 nanotubes fabricated by a modified two-step anodization technique

Bamboo like TiO2 nanotubes were successfully fabricated by a modified two-step anodization technique under different voltage and time. X-ray diffraction patterns and Raman spectra confirmed the anatase crystal phase of TiO2 nanotubes. Optical studies reveal that the band gaps of TiO2 nanotubes shrinked to 2.517(7) eV by varying the anodization parameters. The decrease in band gap was due to the improved crystallinity and the defect states formed in the forbidden gap. The photoluminescence spectra clearly revealed the formation of intermediate defect states, oxygen vacancies and color center defects. Bamboo like nanotubes exhibited higher photocurrent density than stack layered nanotubes due to the increase in crystallinity with higher surface area, enhanced light penetration depth and better scattering within the tubular structure. The photocatalytic activity of TiO2 nanotubes for methyl orange degradation followed pseudo first order kinetics.