Single-step electrochemical anodization for synthesis of hierarchical WO3–TiO2 nanotube arrays on titanium foil as a good photoanode for water splitting with visible light

• TiO2–WO3 nanotubular composite were synthesized by anodization of titanium.
• PEC water splitting of these composite is higher than that of pure TiO2 nanotubes.
• Quantity effect of W in these composite for PEC water splitting is investigated.
• Maximum hydrogen production of 2.14 mL/cm2 after 120 min is obtained.

Hierarchical WO3–TiO2 nanotube (WTNs) composite structures were obtained by anodization of titanium in a single-step process using sodium tungstate as the tungsten source. The resulting WTNs showed tubes with diameters in rang of 80–110 nm, wall thickness of 20–40 nm and tube lengths in the range of 7–8 μm. Diffuse reflectance spectra showed an increase in the visible absorption relative to pure TiO2 nanotubes (TNs). The photo-electrochemical performance was examined under simulated sunlight irradiation in 1 M NaOH electrolyte. Photo-electrochemical characterization shows that tungsten doping efficiently enhances the photo-catalytic water splitting performance of WTNs composite. The sample (WTNs-2) exhibited better photo-catalytic activity than the TNs and WTNs fabricated using other W concentrations. This can mainly be attributed to better charge carrier separation and transportation in photoelectrochemical water splitting by providing an effective way to address recombination losses in these composite materials.

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