Visible-light-responsive Ag-Si codoped anatase TiO2 photocatalyst with enhanced thermal stability

To utilize visible light more efficiently and enhance the photocatalytic performance of TiO2, Ag-Si/TiO2 photocatalyst was synthesized via a two-step method. The obtained materials were characterized by XRD, Raman, TEM, HRTEM, BET, TG-DTA, XPS, ICP as well as UV-vis DRS. All photocatalyst materials held an anatase phase confirmed by XRD, Raman and HRTEM. The Ag-Si/TiO2 photocatalysts possessed high thermal stability and the phase transformation was retarded to about 900 deg. C revealed by XRD and TG-DTA. The Ag-Si/TiO2 particles synthesized via the nonaqueous method were highly monodispersed and the particles size became smaller compared to the un-doped TiO2, resulting in the enlargement of surface area. In addition, UV-vis light absorption shifted to visible region after Ag doping. XPS results demonstrated that Si weaved into the matrix of TiO2 and enriched in the surface layer, while Ag dispersed on the surface of TiO2 particles. The Ag dopant suppressed the recombination of photogenerated electrons and holes, Si enlarged the surface of photocatalysts. Silver and silicon co-doping improved the visible photocatalytic activity, which was evaluated by Rhodamine B (RhB) degradation. The photocatalytic activity of the obtained Ag-Si/TiO2 sample was much more higher than those of pure TiO2 and Ag/TiO2, reaching the maximum at the Ag and Si content of 0.5 mol% and 20.0 mol%, respectively. The improved visible photocatalytic activity may be attributed to the synergetic effects of codoping by silver and silicon.