Photo-electrochemical generation of hydrogen using hybrid titanium dioxide nanotubular arrays

摘要

Anodization of Ti in acidified fluoride solution resulted in a vertically oriented and an ordered nanotubular titanium oxide surface. Annealing of the TiO2 nanotubular arrays in a carbonaceous or nitrogen containing atmosphere presumably resulted in band-gap states, which enhanced the photo-activity. Composite electrode of nanotubular TiO2 + carbon doping resulted in a photocurrent density of more than 2.75 mA/cm2 at 0.2 V(Ag/AgCl) under simulated solar light illumination. The enhanced photo-activity of the carbon-modified nanotubular TiO2 is highly reproducible and sustainable for longer duration. The charge carrier densities, calculated based on the Mott-Schottky analyses, were in the range of 1-3 x 1019 cm-3 for both the carbon modified and the nitrogen-annealed nanotubular TiO2 samples. The asanodized and oxygen-annealed samples showed a charge carrier density of 5 x 1017 and 1.2 x1015 cm-3 respectively. In this study, the measured photo current density was not directly related to the charge carrier densities of the nanotubes. Presence of different phases, such as amorphous, anatase and rutile, influenced the photo activity more than the charge carrier density.