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.