Photocatalytically active Ag-doped TiO₂ coatings developed by plasma electrolytic oxidation in the presence of colloidal Ag nanoparticles

The plasma electrolytic oxidation process of Ti foil in the presence of a colloidal solution of Ag nanoparticles was used for the synthesis of exceptionally photocatalytically active Ag-doped TiO2 coatings. UV-Vis absorption spectroscopy was applied to follow the changes in the surface plasmon resonance band of the Ag nanoparticles as a function of the Ag:PO43 ratio in a phosphate-based electrolyte solution. Transmission electron microscopy revealed the size of the Ag nanoparticles in the range of 3-12 nm. The XRD patterns of the Ag-doped TiO2 coatings confirmed the crystalline anatase TiO2 phase regardless of the dopant concentration and without metallic Ag or crystalline Ag oxide forms. The typical porous morphology of the Ag-TiO2 coatings was observed by scanning electron microscopy. A significantly improved photocatalytic activity of the Ag-TiO2 coatings in the degradation process of the insecticide lindane (gamma isomer of benzene hexachloride) and test molecule methyl orange compared to pure TiO2 was determined using the GC technique. The degradation efficiency of Ag-doped TiO2 coatings is higher for lindane than for methyl orange.