Role of Acetic Acid on Morphology, Structure, Optical Properties, and Photocatalytic Activity of TiO₂ Obtained by Sol-Gel

Titanium oxide (TiO2) is of great interest for the manufacture of solar cells, hydrogen production and for the photodegradation of organic compounds. The synthesis variables, as well as the type of method, affect the morphology, texture, crystalline structure, phase mixtures of TiO2, and in turn, these affect the optical and catalytic properties of TiO2. In this work, the role of acetic acid as a catalyst and chelating agent on morphology, texture, crystal structure, optical properties, and photocatalytic activiy of TiO2 samples obtained by sol gel method assisted with sodium dodecyl sulfate as template was investigated. The results obtained indicated that acetic acid, in addition to catalyzing the hydrolysis of the TiO2 precursor, acts as a chelating agent causing the decrease of the crystallite size from 18.643 nm (T6 sample, pH=6.8, without addition of acetic acid) to 16.536 nm (T2 sample, pH=2). At pH values of 2 and 3, only the anatase phase is formed (T2 and T3 samples), whereas at pH values 5 and 6.8, in addition to the anatase phase, 11.4% and 15.61% of the brookite phase is formed (T5 and T6 samples, respectively). The band gap of TiO2 decreased with the decrease of the pH used in its synthesis. Although T2 sample has the highest values ​​of specific surface area and pore volume (232.02 m2g-1 and 0.46 gcm-3, respectively), sample T3 had better efficiency in methylene blue dye photodegradation.