Characterization of nitrogen and fluorine co-doped titania photocatalyst: Effect of temperature on microstructure and surface activity properties

Nitrogen and fluorine co-doped titania photocatalyst samples to be used for air purification were prepared by spray pyrolysis using a mixed solution of TiCl4 and NH4F. Droplets of the mixed solution formed by nebulizer passed through a ceramic tube furnace under a suction of an aspirator and a titania-based powder was formed at temperatures in the range from 700 to 1000 °C. The resulting nanopowders were characterized by electron microscopy, X-ray diffraction, temperature programmed desorption of NH3, methods of thermal analysis, particle size, surface area and porosity determination by nitrogen adsorption. Morphology and surface activity of the samples prepared at various conditions were compared. The thermal behavior of the samples characterized by TG, DTA and ETA under air heating conditions is discussed considering the differences in samples preparation. A high photocatalytic activity for acetaldehyde decomposition in a visible region of spectrum depended on the spray pyrolysis temperature and can be ascribed to a synergetic effect of nitrogen and fluorine doping.