Photoelectrochemical response studies of W deposited TiO2 nanotubes via thermal evaporation technique

Abstract

Titania (TiO2) nanotube arrays were successfully formed by anodising titanium (Ti) foil in a standard two-electrode bath in 1 M of glycerol (HOCH2CH(OH)CH2OH) containing 0.5 wt% ammonium fluoride (NH4F). It was observed that such anodisation condition resulted in self-organised of TiO2 nanotubes with the average pore sizes of approximately 90 nm and the length was approximately 1 µm. In this study, various thicknesses of tungsten (W) were deposited on TiO2 nanotubes via thermal evaporation technique to investigate the photoelectrochemical (PEC) response and hydrogen generation rate. The improvement in PEC response was found by using a photoanode of 2.5 nm W deposited TiO2 nanotubes as compared to the pure TiO2 nanotubes. It was believed that a shallow trap was provided for charge carrier to inhibit the recombination and eventually extend the lifetime of charge carrier. In contrast, the higher deposition of W on TiO2 nanotubes resulted in lower PEC response because it acts as charge carrier recombination center. The experiment results show that the maximum photocurrent density of 0.9 mA/cm2 and maximum hydrogen production rate of 12 µL/cm2/min was achieved using 2.5 nm W deposited TiO2 nanotubes.