Photocatalytic deposition of Ag nanoparticles on TiO₂: Metal precursor effect on the structural and photoactivity properties

A series of 1wt.% Ag-TiO₂ photocatalysts were obtained by photodeposition using different organic (acetylacetonate, Ag-A) and inorganic (nitrate, Ag-N, and perchlorate, Ag-C) silver precursors in order to determinate the influence of the silver precursor on final properties of the photocatalysts. The resulting photocatalytic materials were characterized by different techniques (UV-Vis DRS, TEM/HRTEM and XPS) and their photocatalytic activity was evaluated in the degradation of rhodamine B (used as model pollutant) in aqueous solution under simulated solar light. The photocatalytic reduction of Ag species to Ag⁰ on TiO₂ was higher with silver nitrate as precursor compared to acetylacetonate or perchlorate. All the Ag-modified TiO₂ photocatalysts exhibited a surface plasmon resonance effect in the visible region (400-530nm) indicating different metal particle sizes depending on the Ag precursor used in their synthesis. A higher photocatalytic activity was obtained with all the Ag/TiO₂ samples compared with non-modified TiO₂. The descending order of photocatalytic activity was as follows: Ag-A/TiO₂≈Ag-N/TiO₂>Ag-C/TiO₂>TiO₂-P25. The enhanced photoactivity was attributed to the presence of different amounts Ag⁰ nanoparticles homogeneously distributed on Ag₂O and TiO₂, trapping the photogenerated electrons and avoiding charge recombination.