Cerium-doped TiO2 thin films: Assessment of radiation absorption properties and photocatalytic reaction efficiencies in a microreactor

The photocatalytic activity of different TiO2 films for the degradation of 17-alpha-ethinylestradiol (EE2) in aqueous solution was studied using a continuous flow, planar microreactor. Pure and cerium-doped TiO2 films, prepared by the sol-gel method, were tested under simulated sunlight. The influence of the cerium content on the radiation absorption properties of the films and on the photocatalytic oxidation of EE2 was investigated. The performances of the catalytic films were objectively assessed by means of the absorption efficiency parameter and the quantum efficiency parameter. Spectral diffuse transmittance and reflectance measurements of the films were carried out to evaluate the fraction of radiation absorbed by the coatings. Although the film with 0.8 nominal atomic % of cerium (Ce at%) showed the highest absorption efficiency, it was the less efficient in terms of pollutant degradation, even less than the undoped catalyst. The most efficient photocatalytic film to degrade EE2 was the sample with 0.3 Ce at%. The benefits of employing a microreactor for catalyst screening are demonstrated, allowing the study of different operating conditions in a simple and fast way, and with minimum consumption of reagents.