Tailoring the morphology of TiO2 nanotube arrays: Independent effect of tube's morphology on its photoelectrocatalytic efficiency during water splitting

The morphology of titania nanotube arrays (TNAs) fabricated by anodization was controlled to investigate its effect on the photoelectrochemical (PEC) performance of this nanomaterial, of interest in various applications including water splitting, wastewater treatment and sensing. Morphology was controlled by two-step anodization and by systematically varying electrolyte composition and anodization time. TNA surface was uniform at different anodization conditions, and TNAs' length (3-15 mu m range) and wall thickness (12-110 nm) and diameter (50-300 nm) were varied independently. It was observed that PEC efficiency under UVA light improves with diameter and wall thickness until reaching a plateau. PEC efficiency increases and then decreases upon changing tube length. A maximum PEC efficiency of 18.6% was achieved using titania nanotube arrays with tube length, external diameter and wall thickness of 9 +/- 1.4 mu m, 150 +/- 8 nm and 50 +/- 2 nm, respectively.