Ceria promotion of acetaldehyde photo-oxidation in a TiO2-based catalyst: a spectroscopic and kinetic study

Abstract

A spectroscopic and kinetic study of the photo-oxidation of acetaldehyde with a CeO₂–TiO₂ composite catalyst is presented. Both UV and visible illumination conditions were tested. The study focuses on analysing the role of ceria in the photocatalytic behaviour by contrasting the CeO₂–TiO₂ behaviour with that of the appropriate TiO₂ reference. To this end, we developed an intrinsic kinetic expression with explicit inclusion of the effect of photon absorption on the reaction rate as well as a reaction scheme proposed on the basis of combined Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and Electron Paramagnetic Resonance (EPR) characterization. The combination of spectroscopic and kinetic tools provides quantitative evidence that the oxide–oxide contact controls the activity of the composite catalyst through the number of hole-related species able to attack the pollutant, this in turn being related to the influence of ceria defects on charge carrier fate. The abovementioned key properties controlling photoactivity are the same for UV and visible excitation, producing a highly active photocatalyst suitable for sunlight applications.