Sn modification of TiO2 anatase and rutile type phases: 2-Propanol photo-oxidation under UV and visible light

In this work binary Sn-Ti samples having Sn:Ti atomic ratios from zero to one were prepared through a hydrothermal method. The resulting high surface area powders were characterized using a combination of X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, UV-vis spectroscopy and porosimetry techniques. The series of samples covers catalysts with anatase and rutile type structures. Each sample is composed of a main (anatase or rutile) Ti1-xSnxOy phase decorated by different Sn-containing entities. The photo-catalytic performance in the 2-propanol photo-oxidation was assessed through the measurement of the reaction rate and true quantum efficiency. The latter required the measurement of the optical properties of the powders and the computation of the local superficial rate of photon absorption. Although relatively similar activity maximum can be obtained for anatase and rutite type samples based in the comparison of the reaction rates, the calculation of the true quantum efficiency demonstrates that the optimum anatase type material displays superior performance than the rutile one. The physico-chemical origin of this behavior is analyzed in terms of the electronic and structural properties of the binary Sn-Ti samples.