Visible light photoelectrochemical and water-photoelectrolysis properties of titania nanotube arrays

We examine the visible light water-photoelectrolysis and photoelectrochemical properties of highly ordered titania nanotube arrays as a function of nanotube crystallinity, length (up to 6.4 μm), and pore size. Most noteworthy of our results, under visible light AM 1.5 illumination (100 mW/cm2) the titania nanotube array photoanodes (1 cm2 area), pore size 110 nm, wall thickness 20 nm, and length 6 μm, generate hydrogen by water photoelectrolysis at a rate of 175 μL/h, with a photoconversion efficiency of 0.6%. The energy–time normalized hydrogen evolution rate is 1.75 mL/h W. The oxygen bubbles evolving from the nanotube array photoanode do not remain on the sample, hence the output remains stable with time irrespective of the duration of hydrogen production.