Band gap engineering of nanotubular Fe2O3-TiO2 photoanodes by wet impregnation

Abstract Due to many limitations of titanium oxide, its direct use in photoelectrochemical water splitting under solar radiation is ineffective. Band gap engineering based on introduction of the Fe2O3 phase into TiO2 by wet impregnation has been proposed. In particular, nanoporous anodic titanium oxide layers were soaked in solutions with different concentrations of iron ion (5–100 mM) followed by their air annealing at 400 °C. As-prepared nanotubular Fe2O3-TiO2 materials were characterized by using field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), Raman spectroscopy, X-ray diffraction (XRD), reflectance measurements, Mott-Schottky analysis, and photoelectrochemical tests. It was found that increasing the iron content in anodic materials strongly affects their resulting semiconducting and photoelectrochemical properties. The maximum of generated photocurrent shifts towards visible light as the band gap energy decreases (from 3.36 to 2.89 eV) with the respect to increasing the iron content in the anodic materials.