Silver-modified titanium dioxide thin films for efficient photodegradation of methyl orange

摘要

Silver-modified, rought, high surface area titanium dioxide thin films resulting via a two-step dipping and UV-irradiation process were examined for their catalytic activity towards photodegradation of methyl orange (MO). Optimization of the photocatalyst's performance as a function of the dipping time, irradiation time and the dipping solution concentration was performed. The optimum silver nitrate concentration of the dipping solution was found to be 10~(-3) M. The modified materials present enhanced photocatalytic efficiency and can decompose the organic pollutant three-times faster than the undoped original films (Degussa P25). A further Ag~+- ion concentration increase in dipping solution results a decrease of the films photocatalyst efficiency due to a shading to the available semiconductor surface by the silver layer. This performance is consistent with the unique structural, morphological and surface characteristics of the composite silver/titania materials. The lower the average particle size, roughness and fractal dimension, the higher the photodegradation percentage and the on the basis of a mechanism involving efficient separation of electron-hole pairs induced by silver-ions (Ag~+). Reproducibility tests proved that the photocatalytic activity of the silver-modified films remains intact even after six consecutive experiments of new added popullant quantities.