Measuring and interpreting quantum efficiency of acid blue 9 photodegradation using TiO2-based catalysts

Abstract

A series of highly-active catalysts were obtained from the same precursor and calcined at different temperatures to generate single-phase anatase and anatase-rutile composite powders. Performance of the catalysts was compared with the P25 reference and assessed through the measurement of the optical properties of the materials and calculation of the efficiency of the photodegradation of a multifunctional dye, acid blue 9. X-ray diffraction, porosimetry, UV–vis and photoluminescence spectroscopies were used to analyze the physico-chemical properties of the catalysts and to test their stability under reaction conditions. Through the calculation of the reaction rate and total organic carbon (TOC) observables as well as the apparent and true quantum efficiency parameters we analyzed quantitatively the performance of the materials. We observe that a high surface area anatase sample showed optimum activity and adequate selectivity towards full mineralization. The catalysts were subjected to sedimentation and recycling experiments and the catalytic performance compared on the basis of the true quantum efficiency. The use of this last parameter leads to different conclusions than those supported by an analysis based in the kinetic constant, reaction rate or apparent quantum efficiency. The high quantum efficiency and easy recovery after repeated experiments shown by the catalysts were interpreted on the basis of the characterization results.