Photoactivity of titanium dioxide/carbon felt composites prepared with the assistance of supercritical carbon dioxide: Effects of calcination temperature and supercritical conditions

Abstract

TiO2-coated carbon felt (TCF) composite catalysts have been prepared via a supercritical treatment of titanium tetraisopropoxide (TTIP) as the precursor. The physical properties of the catalysts were characterized by means of thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), fluorescence spectroscopy, scanning electron microscopy (SEM), and BET surface areas techniques. The photocatalytic activities of the materials were evaluated using the degradation of Congo red (CR) as a probe reaction. All the composites showed much higher photocatalytic activity than commercial P25 due to significant synergistic effects. Reused TCF retained high photocatalytic activity for degradation of CR. The photocatalytic efficiency in CR degradation was found to be strongly dependent on the TiO2-coating ratio and calcination temperature. A possible mechanism for the enhanced reactivity involves shuttling of electrons from TiO2 particles to the carbon felt (CF) as a result of an optimal arrangement in TCF that stabilizes charge separation and reduces charge recombination. In addition to the significant synergistic effects, the abundant spaces between adjacent carbon fibers allow UV light to penetrate into the felt-like photocatalyst to a considerable depth, so that a three-dimensional environment is available for the photocatalytic reaction.