Photothermocatalytic Synergetic Effect Leads to High Efficient Detoxification of Benzene on TiO2 and Pt/TiO2 Nanocomposite

Abstract

Controlling the emission of volatile organic compound (VOCs) has become an important issue because they are not only hazardous to human health but also harmful to the environment. Among various VOCs, the carcinogenic and recalcitrant benzene, which is one of the most abundant aromatic hydrocarbons found in polluted urban atmospheres, has been regarded as a priority hazardous substance for which efficient treatment technologies are needed. Heterogeneous photocatalysis based on nanostructured TiO2 has attracted much research attention in the past decades as an important and promising technology for the detoxification of organic pollutants because of the superior photocatalytic activity, chemical stability, low cost, and nontoxicity of TiO2. However, when TiO2 photocatalysts are applied to the detoxification of benzene in the gas phase, they are prone to deactivation mainly due to the deposition of less reactive byproducts on the TiO2 surface, making the photocatalytic detoxification of benzene very inefficient. 4] Much effort has therefore been devoted to enhancing the efficiency of benzene photocatalytic oxidation. The modification of TiO2 with noble metal (e.g. , Rh and Pt) as co-catalysts has been found to boost the efficiency of benzene photocatalytic oxidation and improve the durability of TiO2 catalysts. Recently, photocatalytic oxidation combined with ozone oxidation on TiO2 has been developed to improve the efficiency of benzene or toluene oxidation. As ozone is also an air pollutant, additional setup was required to remove the its excess. Plasma-driven photocatalysis and catalysis have been reported to enhance VOC decomposition activity on TiO2 and Al2O3. [10] Developing a highly efficient and cost-effective strategy for the detoxification of recalcitrant VOCs, such as benzene, has been a great challenge. Herein, photocatalysis and thermal catalysis have been ideally combined together just by a facile method of coating TiO2 catalyst and Pt/TiO2 nanocomposite on the surfaces of a UV lamp without using any additional heater, by which both UV irradiation and nonradiative thermal energy emitted from the UV lamp are fully used, and the high efficient photothermocatalytic detoxification of benzene has been realized. In this perfect combination of photocatalysis and thermal catalysis, a new photothermocatalytic synergetic effect has been found for the first time. Various high-pressure Hg lamps have been widely used as UV light sources in photocatalytic studies for decades. However, their nonradiative thermal energy emitted has not been fully used. In the closed gas-phase reactor, when the selfrectified high-pressure Hg lamp was turned on, the thermal energy emitted from the lamp made its surface temperature automatically increase to 240 8C, which provided a possibility for photothermocatalytic oxidation to occur without using an additional heater. The TiO2 sample was coated on the surfaces of the lamp, and thus the TiO2 catalyst was co-excited by both UV irradiation and thermal energy. Under the photothermocatalytic condition, benzene was rapidly oxidized with time and