Synthesis, Characterization, and Photocatalytic Testing of Titania-Based Aerogels for the Degradation of Volatile Organic Compounds

The need to degrade volatile organic compounds (VOC’s) has grown with recent economic and environmental concerns. Advanced oxidation processes governing breakdown of VOC’s have received significant attention due to environmentally conscious practices and objectives. Photocatalysis is a logical approach for VOC removal in air because of minimal energy requirements and ease of implementation. Titania with high pore volume and surface area are synthesized using a modified sol-gel method in conjunction with carbon dioxide supercritical drying. Vanadium doping increases the visible absorption of titania aerogels. Solvent removal is achieved using a custom-built high pressure chamber designed for carbon dioxide supercritical drying. This method preserves pore structure of the sol-gels and results in low density monoliths. Characterization of the materials suggests photoactivity based on high surface area, nanoscale morphology, absorption spectra, and crystallinity. The aerogels were characterized by X-ray powder diffraction (XRD), UV-Visible diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDXS), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), and Brunauer-Emmet-Teller (BET) physisorption surface analysis. Materials were tested for activity in degrading propionaldehyde, a model VOC, under ultraviolet light using a flow-through type quartz plate reactor and gas chromatograph. Titania and vanadium-doped titania aerogels exhibited propionaldehyde degradation at a rate of 1.04 µ-molcm-2h-1 confirming the materials as active gas-phase photocatalysts.