Optimizing Nanoscale TiO2 for Adsorption-Enhanced Photocatalytic Degradation of Low-Concentration Air Pollutants

Adsorption and photodegradation are key steps in environmental air purification. Micropores have been introduced into anatase TiO2 nanocatalysts to enhance the adsorption of pollutant molecules onto the photocatalyst surface, which increases the use of the photoinduced electron-hole pairs. Three nanocomposites have been synthesized with dodecylamine as a pore-forming agent under mild hydrothermal conditions and at varying temperature of preparation. Samples synthesized at 100, 115, and 130 degrees C, labeled TiO2-100, TiO2-115, and TiO2-130, respectively, provided insights into the effect of crystallinity and micropore area on the removal efficiency of gas-phase organic pollutants. Of the three, TiO2-100 had the largest micropore area (493m(2)g(-1)) but amorphous phase. TiO2-130 had anatase phase but only mesopores, whereas TiO2-115 had both a relatively large micropore area (258m(2)g(-1)) and an anatase crystal structure. Toluene was chosen as a model air pollutant. Experiments were performed in a single-pass reactor in the presence of UV irradiation under various experimental conditions, such as varying partial pressures of toluene, contact times, and relative humidities of the mobile gas phase, to approximate realistic conditions for this air purification system. Of the three prototype catalysts, TiO2-115 showed the highest removal and mineralization efficiencies owing to the optimized availability of photogenerated holes and adsorbed toluene. The key parameters for optimized photocatalysis of low-concentration air pollutants are the micropore area and the crystallinity of the photocatalyst.