Ultra-thin SiO2 layers on TiO2: improved photocatalysis by enhancing products' desorption.

A study on the photocatalytic degradation of contaminants (salicylic acid and stearic acid) on titanium dioxide films overcoated with a few monolayers of silica is presented herein. A rather uncommon situation was observed, where the presence of the thin silica layers decreased the degradation rate of stearic acid while increasing that of salicylic acid. The results were explained by addressing the effect in the presence of silica films on the desorption of the intermediate products formed in the degradation of salicylic acid.