The effect of anodization parameters on the formation of nanoporous TiO₂ layers and their photocatalytic activities

Highlights: • Nanoporous TiO₂ layers were formed on titanium surfaces by anodization. • Effects of such parameters as voltage, temperature and time investigated in details. • 20 °C, 30–40 volts and 240 minutes were determined as the optimum parameters. - Abstract: In this work, nanoporous titanium dioxide (TiO₂) layers were successfully formed by electrochemical anodization method on titanium (Ti) surface in fluorine containing electrolytes with different processing parameters. The effects of anodization voltages, electrolyte temperature and anodization time on the microstructure and photocatalytic performance of nanoporous TiO₂ layers were investigated and compared in details. Nanoporous structures were annealed at 480 °C for 2 h in air in order to obtain anatase transformation and increase crystallinity. The phase structure and surface morphology of the samples characterized by means of X-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. The photocatalytic activity tests of the samples were evaluated by the degradation of aqueous methylene blue (MB) solutions under UV light illumination for different periods of time. The results showed that the processing parameters on production of nanoporous TiO₂ layers played important roles in the degradation of aqueous MB solutions. To sum up, the highest photocatalytical activity was obtained at the sample anodized under 30 V for 30 min at 20 °C among the samples