Intrinsic defects generated by iodine during TiO2 crystallization and its relationship with electrical conductivity and photoactivity

Defect formation during synthesis is one of the strategies used to improve the photoactivity of polycrystalline semiconductors such as titanium dioxide (TiO₂). Defects can modify the electronic structure of TiO₂ and change the surface of the interaction between the photocatalyst and the reactants. In this study, TiO₂ relationship between processing in the presence of iodine and the consequent formation of intrinsic defects were explored. TiO₂ nanoparticles were synthesized using the polymeric precursor method and exposed to iodine ions at concentrations up to 5 mol%. After calcination at 350°C, detailed chemical analyses revealed that iodine was absent in the samples. However, the TiO₂ properties, such as specific surface area, crystallite sizes, and specific grain boundary area, were affected. Further experiments, such as electron paramagnetic resonance, diffuse reflectance, optical measurements, and electrochemical impedance spectroscopy indicated the presence of defects in the iodine-processed samples. These defects directly influenced the electrical properties of the material, which affected the photoactivity, measured by the degradation of acetaminophen.