Decoration of vertically aligned TiO2 nanotube arrays with WO3 particles for hydrogen fuel production

WO₃ decorated photoelectrodes of titanium nanotube arrays (W-oxide TNTAs) were synthesized via a two-step process, namely, electrochemical oxidation of titanium foil and electrodeposition of W-oxide for various interval times of 1, 2, 3, 5, and 20 min to improve the photoelectrochemical performance and the amount of hydrogen generated. The synthesized photoelectrodes were characterized by various characterization techniques. The presence of tungsten in the modified TNTAs was confirmed using energy dispersive X-ray spectroscopy (EDX). Field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscope (HRTEM) proved the deposition of W-oxide as small particles staked up on the surface of the tubes at lower deposition time whereas longer times produced large and aggregate particles to mostly cover the surface of TiO₂ nanotubes. Additionally, the incorporation of WO₃ resulted in a shift of the absorption edge toward visible light as confirmed by UV-Vis diffuse reflectance spectroscopy and a decrease in the estimated band gap energy values hence, modified TNTAs facilitated a more efficient utilization of solar light for water splitting. From the photoelectrochemical measurement data, the optimal photoelectrode produced after 2 min of deposition time improved the photo conversion efficiency and the hydrogen generation by 30% compared to that of the pure TNTA.