Photoelectrocatalysis of MtBE vapor via TiO2 and TiO2/CuO composite thin-film photocatalysts

• Main Authors: Zih-Rong Chiu, 邱姿蓉
• Other Authors: Chung-Hsuang Hung
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/64299926983027452281

碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程研究所 === 102 === Photocatalytic oxidation processes are often applied to control volatile organic compounds (VOCs), which use semiconductor oxides as photocatalysts to yield electron-hole pairs on their surfaces while irradiated with suitable light energy. Producing highly reactive species, such as, hydroxyl and superoxide radicals is considered as key mechanisms for fast degradation of hazardous air pollutants (HAPs). But, due to the fast recombination of the electron-hole pairs, the degradation rates of many VOCs are not high enough and have low quantum efficiencies. Accordingly, this study aimed to develop a gas-phase photoelectrocatalytic reaction process by providing additional biases to photocatalytic oxidation processes for achieving low recombination rates of electron-hole pairs and high degradation rates of VOCs. Other than preparing various kinds of photocatalysts with different characteristics, several affecting factors including reaction temperature, water vapor content, applied biases were also evaluated in this study. Methyl tert-butyl ether (MtBE) was tested as a target compound in this research. The experimental results demonstrated a higher MtBE degradation rate achieved in external bias assisted photocatalytic reactions than in no bias assisted ones. The degradation of MtBE in these reactions followed a pseudo first-order reaction kinetic. For the effects of operation conditions, the MtBE degradation rate increased with reaction temperature and humidity initially, but it declined for further increasing temperature and humidity. Similar reaction patterns were also observed for the effects of the external bias on the degradation rate of MtBE. All of these results indicated the adsorption phenomena dominantly affect the photocatalytic degradation rate of MtBE. Both increase in temperature and humidity can enhance surface reaction rate of MtBE on TiO2, but reduce the adsorption of MtBE by TiO2. As a result, while temperature and humidity changing, peak reaction rates for MtBE were detected due to the compromised results of enhanced surface reaction rate but reduced adsorption rate for MtBE. Two kinds of thin-film photocatalysts, pure TiO2 and CuO-composited TiO2, were prepared in this study. The later one kept high activities while using visible light as light sources, but the former one had higher photocatalytic activities than the later one wile irradiated with near-UV light. In addition, due to more photo-generated electrons transported away from catalysts and their electron-hole recombination rates were reduced, higher MtBE degradation rates were achieved when the catalysts embedded with less narrow spacing of comb-shape circuits.