Preparation of gold-modified F,N-TiO₂ visible light photocatalysts and their structural features comparative analysis

TiO₂ doped with F and N ions and modified with gold nanoparticles was prepared via sol–gel technique. Au modifier was added either by impregnation method or during synthesis of F,N-TiO₂. The microstructure, phase and element compositions of the obtained materials were examined by various techniques, such as XRD, nitrogen sorption, SEM, TEM, and XPS. The structure of TiO₂ was not influenced by the method of Au particles introduction. But the nature of gold nanoparticles distribution in the resulting material depends on the modification method. Impregnation resulted in Au nanoparticles predominantly located on F,N-TiO₂ surface. These species was easily detected by SEM and XPS. The presence of catalytically active forms, i.e. Au⁰ + Au³⁺, was shown. Au nanoparticles added into the reaction mixture during TiO₂ synthesis process influenced its lattice microstresses. It results in strong Au-support interaction and more efficient charge carrier separation. F,N-TiO₂ modified during its synthesis has shown the highest photocatalytic activity among all samples under visible light irradiation.