Preparation and photoelectrochemical characterization of WO3-loaded TiO2 nanotube arrays via radio frequency sputtering

Titanium dioxide (TiO2) nanotubes loaded with tungsten trioxide (WO3) were prepared using the radio-frequency (RF) sputtering technique to enhance the photoelectrochemical (PEC) water-splitting process. The incorporation of tungsten ions (W6+) onto the TiO2 nanotubes at a sputtering time of less than 1 min dominated the formation of hybrid WO3–TiO2 nanotubes, as manifested by the formation of the WOTi bond. A long deposition time resulted in the accumulation of W on the nanotube surfaces and initiated the growth of a cauliflower-like structure. The resultant hybrid nanotubes exhibited significantly enhanced visible spectrum absorption and higher photoconversion efficiency compared to the pure TiO2 nanotubes. Hybrid WO3–TiO2 nanotubes deposited for 0.5 min exhibited a high photocurrent density that reached 1.6 mA/cm2, with a photoconversion efficiency of 2.65%. This behavior is attributed to the faster transport of photogenerated electron/hole pairs, which prevented backward reactions and reduced the number of recombination centers.