2.2. Preparation of Polypyrrole-TiO2 Nanocomposite

The polypyrrole-TiO₂ (PPy-TiO₂) nanocomposite was synthesized via in situ polymerization of pyrrole monomer and TiO₂ nanoparticles in the presence of ferric chloride (FeCl₃) as an oxidizing agent [36]. First, TiO₂ was added to 1 M of HCl aqueous solution and placed into an ice water bath after ultrasound for 1 h. Then, a certain amount of pyrrole monomer was added and stirred continuously for 2 h to make the pyrrole monomer fully adsorbed on the surface of TiO₂. In addition, a certain amount of FeCl₃ was fully dissolved in 1 M HCl aqueous solution, where the molar ratio of pyrrole monomer and FeCl₃ was maintained at a 1:2 ratio. The FeCl₃ acid solution was slowly dropped into the mixed acid solution of TiO₂ and pyrrole monomer, and after continuous agitation for 4.5 h, filtration, washing, and drying, PPy-TiO₂ material was obtained. According to the above method, the PPy-TiO₂ composites were prepared using different additive amounts of pyrrole, and the molar ratios of PPy:TiO₂ were 0; 1:125; 1:100; 1:75; 1:50, respectively.