Valérie Keller

Synthesis and characterization of a new medium surface area TiO2–β-SiC material for use as photocatalyst

A new medium surface area and non-microporous TiO2–β-SiC photocatalytic material was successfully obtained according to an extension of the Shape Memory Synthesis (SMS) method, and following a three step procedure. A high surface area TiO2 supported on an activated charcoal precursor was prepared in a first step by the sol–gel precipitation of titanium tetraisopropoxide in the presence of activated charcoal powder. The second step consisted of a gas–solid reaction between this precursor and SiO vapors at 1300 °C under dynamic vacuum which formed TiC–β-SiC, by carboreduction of SiO vapors and TiO2 into β-SiC and TiC respectively. The final step was oxidation in air at temperatures ranging from 420 °C to 600 °C which produced the TiO2–β-SiC material, using the high resistance of β-SiC towards oxidation to selectively form TiO2. The gross morphology of the activated charcoal precursor was maintained during the carburization and the subsequent oxidation processes according to the SMS concept. Both TiO2 and the β-SiC semiconductor phases were in intimate contact in the same grain of catalyst, without the usually problematic post-synthesis shaping of high mechanical strength SiC-based materials and using no binder. The TiO2-to-SiC ratio could be directly tuned by adjusting the TiO2 content of the precursor, whereas the anatase-to-rutile ratio could be modified by changing the post-synthesis calcination temperature, without altering the β-SiC properties or significantly increasing the average TiO2 particle size.