Performance Of Pt Modified Microporous TiO₂ For Purifying Indoor VOCs

TiO₂ photocatalysis is a promising technology for VOCs purification. Insufficient mineralization and release of harmful byproducts are the two major challenges of photocatalytic VOCs purification in practical application, and greatly restrict the promotion of this technology. Conventional catalysts exhibit insufficient adsorption efficiency of VOCs at indoor concentration level（ppb^ppm） and thus inhibit subsequent photocatalytic reaction. Byproducts can easily desorpt from the surface of TiO₂ into the gas phase. To enhance the mineralization efficiency and reduce the byproducts release, microporous TiO₂ with large surface area was prepared as the substrate to load Pt. Adsorption and photocatalytic oxidation behavior of Pt modified microporous TiO₂ were studied through structural characterization and toluene adsorption-photocatalysis experiments. Moreover, substrate effect of microporous TiO₂ and synergy mechanisms by Pt modification were studied. The main results are as follows:（1） Amorphous microporous TiO₂（T-90） was prepared by low temperature hydrothermal method. The specific surface area of T-90 was 14.9 times larger than that of P25, with the microporous area accounting for 88.7%. The equilibrium adsorption amount and mineralization efficiency of toluene on T-90 increased by 663.4% and 68.7% compared to P25, showing excellent adsorption and mineralization ability.（2） The effect mechanism of Pt loading on the adsorption and photocatalytic oxidation behavior of toluene was investigated. We prepared Pt modified micro-mesoporous materials by loading Pt on T-90. Microporous TiO₂ provided a large number of strong adsorption sites. The equilibrium adsorption amounts of toluene（5.5 mg/m3） on Pt modified micro-mesoporous materials was 3.8⁴.1 times higher than that of P25. The surface photovoltage of Pt-1.5 was 2.2 times higher than that of T-90. It proved that Pt loading significantly improved the separation efficiency of photogenerated charge carriers. Pt and microporous TiO₂ showed an obvious synergy effect. The mineralization efficiency of toluene on Pt-1.5 was 57.2%, 69.2% and 185.3% higher compared to T-90 and P25. Pt-1.5 also significantly reduced the amount of byproducts such as acetaldehyde, acetone and benzene.（3） The effect mechanism of TiO₂ crystallinity on the adsorption and photocatalytic performance of Pt modified porous TiO₂ was clarified. As the crystallinity of TiO₂ substrates increased,the specific surface area of Pt modified TiO₂ decreased. T-110 had a large specific surface area, high degree of crystallinity and separation efficiency of photogenerated charge carriers. The mineralization efficiency of toluene on Pt modificated T-110 was 77.2%, 14.0% higher compared to Pt modified amorphous microporous TiO₂. The byproducts released from the oxidation process on Pt-110 also reduced significantly at the same time.