Solar water splitting for hydrogen production with Fe2O3 nanotubes prepared by anodizing method: effect of anodizing time on performance of Fe2O3 nanotube arrays

Self-organized iron oxide nanotubes were successfully prepared on the iron foils by a simple electrochemical anodization method in NH4F organic electrolyte. The Fe2O3 nanotubes were characterized by field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, UV–vis absorbance spectra, and X-ray diffraction spectroscopy. Scanning electron microscopy images show that dependent upon the anodizing time, the pore diameters range from 30 to 45 nm. Crystallization and structural retention of the synthesized structure are achieved upon annealing the initial amorphous sample in oxygen atmosphere at 450 °C for 1 h. The crystallized nanoporous film, having a 2.04 eV bandgap, exhibited a maximum photocurrent density of 0.68 mA cm−2 in 1 M NaOH at 0.5 V versus Ag/AgCl. The current potential characteristics showed that the water-splitting photocurrent strongly depends on the anodizing time and its increases with anodization time.