Membrane-Assisted Charge Separation and Photocatalytic Activity in Embedded TiO2: A Kinetic and Mechanistic Study

TiO2 dispersed in polyester acrylate membranes was tested as a photocatalyst in the phenol mineralization reaction assisted by molecular oxygen. Kinetics experiments revealed that, although embedded, the oxide maintains significant catalytic activity. This result was first attributed to the homogeneous dispersion inside the polymeric host of TiO2 nanocrystals, which can be easily irradiated and interact with the reactants. Furthermore, the investigation of the photogenerated charge carriers in the photocatalyst demonstrated that electrons are trapped on Ti3+ centers, while holes are trapped on C-centered species of the polymer matrix. In the presence of O-2, the C-centered radicals of the polymer transform into peroxy radicals, reinforcing the charge separation in the polymer-embedded oxide with respect to the powder. The positive interference of the polymer matrix in reinforcing the electron hole separation is responsible for the relevant photoactivity of the embedded TiO2.