Gas phase 2-propanol degradation using titania photocatalysts: Study of the quantum efficiency

A series of TiO2 samples, prepared by a microwave assisted method followed by spray drying and subjected to further calcination, were tested in gas-phase photodegradation of 2-propanol under UV and Sunlight-type illumination conditions. Samples were characterized using X-ray diffraction, porosimetry, UV-vis and Photoluminescence spectroscopies. This physico-chemical characterization was completed with the in-situ analysis of the sample behavior under illumination conditions using infrared spectroscopy. The photochemical behavior of the samples was analyzed through their reaction rate and particularly efficiency parameters, the later measured as both the apparent and true quantum efficiency. To calculate the efficiency in quantitative basis we carried out a complete analysis of the light-matter interaction in the reaction system as well as the chemical response of the catalysts measuring reaction activity and selectivity. The study measures the differences observed among the most common (including the apparent and true quantum efficiency) approximations used to calculate the efficiency parameter providing evidence that they can differ in a factor of 2-4 and shows that optimum performance in our titania-based catalysts is obtained in presence of anatase-rutile interface contact. However, the analysis of the true quantum efficiency demonstrates that this is not exclusively based in the well-known effect of such interface in charge recombination but also depends critically on the variation of the optical properties of the catalytic solids through the series. (C) 2016 Elsevier B.V. All rights reserved.