Single-step synthesis of Fe-TiO2 nanotube arrays with improved light harvesting properties for application as photoactive electrodes

•Fe-TiO2 nanotubes were synthesized by an innovative single-step anodization method.•The Fe2+ doping of TiO2 nanotubes was induced by the complexing agent DTPA.•Fe-TiO2 arrays developed photocurrent 2.5 times greater than that of the pure TiO2. Research on TiO2 nanotubes gained prominence in the past years due to their photoelectrochemical behavior. Metallic ion doping via a simple and fast method of production can dictate a path in order to achieve and improve such application. This work reports an innovative single-step anodization synthesis of iron-doped TiO2 nanotubes. Titanium foils were anodized at three potentials (20, 40 and 60 V) for 1 h. The resulting arrays were characterized by scanning electron microscopy, X-ray diffraction, Raman, XPS and UV–Vis diffuse reflectance spectroscopy. SEM images showed that higher anodization potentials successfully produced Fe-TiO2 nanotubes without a passivating top-layer. XRD and Raman results indicate that Fe ions were introduced in the anatase framework. Fe-doping produced a shift in the UV–Vis absorption edge towards the visible region, which reflected onto the photoelectrochemical performance of the electrodes. The Fe-TiO2 sample anodized at 60 V developed a current density of 1.9 × 10−4 A·cm−2, i.e., 2.5 times greater than that of the undoped TiO2 sample. The results indicate that the obtained Fe-TiO2 nanotube arrays are promising materials for application as photoactive electrodes.