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

Abstract

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.