電漿子三元複合系統增強二氧化鈦光觸媒效率

Abstract

半導體材料中二氧化鈦(TiO2)是常見的光觸媒,藉由光激發產生電子—電洞 對進而生成具有強活性之自由基去解決有機污染廢水之問題。然而,太陽光譜中僅 有微量的紫外線部分可以被 TiO2 所吸收,而且產生的電子—電洞對的再結合速率 很高,造成 TiO2 在陽光下光催化效率不彰。在本研究中,我們在商用型號 P25 二 氧化鈦中添加了銀奈米粒子和還原氧化石墨烯(RGO)來構建三元複合系統光觸 媒,以提高 TiO2 的光催化性能。我們準備了三種不同幾何形狀的銀奈米結構,包 括球體 (Sphere),十面體(Decahedron)和三角板(Prism)。藉由摻入的銀奈米結 構提供局部表面電漿共振(LSPR)進而增加的可見光之光吸收;除此之外,RGO 的添加更抑制了電子—電洞對之再結合。本研究中,利用實驗搭配模擬系統,採用 時域有限差分法(FDTD)模仿在日光燈照射下,三種不同幾何奈米銀結構所造成 的電場強度分佈,驗證了銀奈米結構的 LSPR 效應。 改質過後的三元複合光觸媒, 以添加十面體奈米銀以及三角板奈米銀效果最具顯著,在白光照射下,顯示出比商 用二氧化鈦光觸媒高 8 倍以上的光催化效率。

TiO2 Nano powder (P25) is the commonly used commercial photocatalyst. However, because only a small ultraviolet portion of solar spectrum can excite the electron-hole pairs and their recombination rate is high, its efficiency is limited. In this study, we added silver nanostructures and reduced graphene oxide (RGO) to construct ternary plasmonic catalyst to improve the catalytic performance of TiO2. We prepared three different geometries of Ag nanostructures including sphere, decahedron and prism. While the incorporated Ag nanostructures led to an increase in light absorption due to localized surface plasmon resonance (LSPR), the RGO inhibited the charge recombination and enhanced the electron-hole separation inTiO2. The finite-difference time-domain method was adopted to simulate the electric field intensity distributions on three different geometries of Ag nanoparticles irradiated by the florescent lamp to verify the corresponding LSPR effects. Both Ag nanodecahedrons/TiO2/RGO and Ag nanoprisms/TiO2/RGO hybrid photocatalysts possessed remarkable photocatalytic activity, which decolorized the dyes up to 80% under white light irradiation for only 1 h and displayed over 8 times higher photocatalytic efficiency than pure TiO2 photocatalyst.