Photocatalytic immobilised TiO2 nanostructures via fluoride-free anodisation

Current methods for anodising titanium to produce immobilised titanium dioxide (TiO2) photocatalysts require the use of hazardous fluoride electrolytes. A fluoride-free electrolyte anodisation method was developed, using bromide- and chloride-based electrolytes and ethylene glycol as an additive. Under optimised anodisation times and temperature conditions, the alternative electrolytes led to the growth of stable immobilised TiO2 nanostructures layers on titanium wires used as a support. Crystal phases and topography of the produced TiO2 layers were characterised using scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoelectron spectroscopy (XPS). The photocatalytic activity of fluoride-free anodised immobilised TiO2 photocatalysts is reported here for the first time, showing that differences in the crystal phases had a strong effect on the degradation of the model aquatic contaminants, carbamazepine and phenol. These results show that effective immobilised TiO2 nanostructures photocatalysts can be obtained using electrolytes without fluorine paving the way to more sustainable and safer production methods for photocatalyst for pollutant abatement in water.