Preparation and Characterization of TiO2 Nanotube Arrays in Ionic Liquid for Water Splitting

Abstract: In the present work, it is described the fabrication and characterization of TiO₂ nantotubes prepared potentiostatically using 1.0 or 5.0 vol.% ionic liquid electrolyte medium at 10 or 20 °C. These experimental conditions led to TiO₂ nanotubes with 63-77 nm pore diameter, crystallite sizes between 27-33 nm, and band-gap values in the 3.1-3.2 eV range. Although the morphology and band-gap values were similar, the water splitting reaction showed differences in terms of photocurrent, up to 300%. Besides, we report also important changes in those parameters related with electronic defects, such as carrier density (N_D), width of depletion layer (w) and Debye length (λ_D). Then, the enhancement on photoelectrochemical properties could be related to a decrease in the rate of surface recombination processes. Finally, these proposition are in agreement with the open-circuit voltage-decay, where was observed a higher electron lifetime for TiO₂NT obtained at higher vol.% of ionic liquid.