Surface CuO, Bi2O3, and CeO2 Species Supported in TiO2-Anatase: Study of Interface Effects in Toluene Photodegradation Quantum Efficiency.

The enhancement of active triggered by surface deposition of Cu, Bi, and Ce containing oxidic species onto a high surface area anatase is analyzed through the calculation of the quantum efficiency for toluene photodegradation under UV and Sunlight-type illumination. To this end, series of Cu, Bi, and Ce containing oxides supported on anatase were synthesized having a growing content of the Cu, Bi, and Ce surface species and characterized with X-ray diffraction and photoelectron, UV-visible, and photoluminescence spectroscopies as well as transmission electron microscopy. Utilizing the surface concentration of Cu, Bi, and Ce species as a tool, we analyzed the influence of the system physicochemical properties affecting quantum efficiency in anatase-based materials. First, employing small surface concentrations of the Cu, Bi, and Ce species deposited onto (the unperturbed) anatase, we provided evidence that all steps of the photocatalytic event, including light absorption, charge recombination, as well as surface interaction with the pollutant and chemical output as to activity and selectivity have significance in the quantitative assessment of the enhancement of the efficiency parameter. Second, we analyzed samples rendering maximum quantum efficiency within all these series of materials. The study indicates that maximum enhancement over anatase displays a magnitude strongly dependent on the efficiency level of calculation and would thus require the use of the most accurate one, and that it occurs through a balance between optoelectronic and chemical properties of the composite materials. The (Cu, Bi, Ce) oxide-anatase interface plays a major role modulating the optoelectronic properties of the solids and thus the efficiency observable.