Low-temperature synthesis and characterization of anatase TiO2 powders from inorganic precursors

Nowadays, it is a great challenge to synthesize crystalline TiO2 using low-temperature methods without a calcination step. In our study, the anatase TiO2 powders were synthesized using titanium tetrachloride (TiCl4) as a precursor via the sol-gel method at low-temperature preparation conditions. Perchloric acid and nitric acid were used as peptizing mediators. The powders were obtained with consequent drying of the sols via evaporation of the solvent. The remaining acid in the powders prevented the aggregation of particles in the aqueous solution. The as-prepared catalysts were characterized by X-ray diffraction, thermal analysis, UV-Vis spectroscopy, BET surface area. The aggregate size of TiO2 in the colloidal suspension solution was measured by dynamic light scattering. Material characteristics were correlated with photocatalytic activities of the prepared samples towards degradation of aqueous phenol solution under UVA radiation. Using HClO4 instead of HNO3 resulted in smaller colloidal particles of TiO2 in the sol and in higher surface area of the powder, while the primary crystallite sizes for both types of powder were similar. The HClO4-based TiO2 had approximately a 1.5 times higher catalytic activity than similar catalysts prepared by using HNO3. Smaller aggregated colloidal particles, and consequently a larger surface area in HClO4-based powder, demonstrate the main reason for better photocatalytic activity compared to the HNO3-based powder.