| Summary: | 碩士 === 國立交通大學 === 環境工程系所 === 99 === In this study, the physicochemical properties and photoreduction behavior of the TiO2 samples doped with 0.01 and 1.00 at.% V ions and calined at different temperatures were investigated. The pure TiO2 exhibited anatase phase at 300 °C and underwent phase transition to rutile one at 600 °C. Incorporation of V ions decreased the transition temperature to 500 °C. Calcination greatly increased the surface V/Ti ratio of the doped TiO2 by 7.6 times as the temperature increased from 200 to 600 牵C. The increase in the surface concentration of the V ions also led to the formation of V2O5 moiety. Doping 1.00 at.% V ions dereduced the bandgap energy of the TiO2 from 3.1-3.3 to 1.6 eV. For oxidation of Rhodamine B, the photocatalysts exhibited the activity in the order of 0.01 at% V-doped TiO2 > pure TiO2 > 1.00 at. % V-doped TiO2. The samples calcined at 500 牵C showed the highest activity for CO2 reduction over other temperatures. CH4 was the only detectable product in the reduction systems. After 1 hr irradiation, the pure TiO2 had the highest quantum efficiency (2.98 %) for CH4 generation, followed by 1.00 at.% V-doped TiO2 (2.65 %) and 0.01 at.% V-doped TiO2 (2.44 %). However, the quantum efficiency of the photocatalysts for CH4 yield after 8 hr irradiation was in the order of 1.00 at.% V-doped TiO2 (0.66 %) > pureTiO2 (0.39 %)~0.01 at.% V-doped TiO2 (0.39 %). The EPR results showed that interfacial charge transfer from the photocatalysts to the adsorbed CO2 and H2O is efficient. Thus, the reduced intermediates determined the low reduction efficiency of CO2 to CH4. The impurity levels locating below the conduction band result in slow reduction kinetics., and the presence of V2O5 moiety at the surface inhibited the reoxidation of CH4.
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