Reactive and morphological trends on porous anodic TiO2 substrates obtained at different annealing temperatures

摘要: Abstract Despite substantial interest on the influence of heat treatment activity anodic TiO2 films, there is still a lack systematic studies addressing differences in photocatalytic and photoelectrochemical performance thermally annealed layers. Here we addressed this problem hierarchical titanium oxide (ATO) layers consisting an outer layer with large pores (rings) inner sub-pores were obtained by three-step anodization titanium. The ATO formed at 20 °C ethylene glycol solution containing 0.38 wt% NH4F 1.79 wt% H2O constant anodizing voltage 70 V. resulting amorphous was 400, 500, 600 °C order to obtain photoactive anatase anatase-rutile mixed phases. characterization performed electron scanning microscopy (SEM/EDS), X-ray diffraction (XRD), low-temperature nitrogen sorption measurements (BET surface area), electrochemical impedance spectroscopy (EIS). A gradual decrease BET area observed increasing annealing temperature due clogging from sintering grains. EIS study Mott-Schottky analysis suggested that conductivity changed reduced fluorine content layer, donor densities decreasing 1.78 ⋅ 10 18 cm − 3 4.08 17 . Raising also caused shift flat band potential towards more negative values, which correlated increase rutile consequently gap 3.26 eV 3.09 eV. studied under pulsed UV illumination. highest photoconversion efficiencies for wavelength 350 nm sample dominant content. degradation methyl red toluidine blue dyes 500 °C. After 9 h, total removal each dye about 80% carbon (TC) 55.3% observed.