Role of Interface Contact in CeO2-TiO2 Photocatalytic Composite Materials

The role of interface contact between two oxides, CeO2 and TiO2, for the photocatalytic elimination of toluene is examined in a series of samples with variable quantities of ceria. Samples having ceria contents in the 1 to 10 mol % range improve significantly, exhibiting up to 3.5 times the activity of the bare nano-TiO2 catalyst. To interpret the photocatalytic behavior, this contribution develops a novel spectro-kinetic approach where a joined analysis of the kinetics of the reaction and the fate of charge charriers is merged with the mathematical modeling of the light catalyst interaction at the photoreactor. This produces a self-consistent approach that simultaneously validates the kinetic model and interprets the activity on rigorous bases. The study is completed with a multitechnique examination of the solids using X-ray diffraction and electron paramagnetic resonance, UV-vis, and X-ray photoelectron spectroscopies as well as high-resolution transmission electron microscopy. The results provide quantitative evidence that the oxide-oxide contact controls the photoactivity through the number of hole-related species available at the surface of the composite materials and that this number is in turn related to the stabilization of reduced Ce species present at the Ce-Ti interface.