Effect of the redox treatment of Pt/TiO2 system on its photocatalytic behaviour in the gas phase selective photooxidation of propan-2-ol

Several titania systems were synthesized by the sol–gel method using two different titanium precursors (titanium isopropoxide or tetrachloride) and diverse ageing methods (magnetic stirring, sonication, reflux and microwave radiation). Screening of such different synthetic conditions led us to choose titanium isopropoxide as the titanium precursor and sonication as the method of choice for ageing the gel. Application of the method to the synthesis of a platinum-doped system resulted in a solid with a BET surface area of 57 m2/g and consisting of 100% anatase titania. The system was submitted to different oxidative and reductive treatments in order to study the effect of such treatments on catalytic performance in gas-phase selective photooxidation of propan-2-ol. Interestingly, both oxidation and reduction at 850 °C led to an increase in molar conversion and selectivity to acetone as compared to calcination at 500 °C. So much so, that oxidation at 850 °C either in synthetic air flow or in static air resulted in better catalytic performance than Degussa P25, despite the fact that our catalysts consisted in very low surface area (6–8 m2/g) rutile titania specimens. XPS analyses of the systems showed that thermal treatment at 850 °C resulted in electron transfer from titania to Pt0 particles through the so-called strong metal-support interaction (SMSI) effect. Furthermore, the greater the SMSI effect, the better the catalytic performance. Improvement in photocatalytic activity is explained in terms of avoidance of electron–hole recombination through the electron transfer from titania to platinum particles.