可見光誘導Ag/AgX等離子體光催化凈化NO的性能與機理

貴金屬納米顆粒的表面等離子共振效應使之在可見光區表現出顯著的特徵吸收。在可見光的誘導下，銀/鹵化銀(Ag/Ag X,X=Cl,Br,I)復合物在污染物凈化中表現出了優良的光催化性能。本研究採用室溫沉澱法制備了Ag/Ag X等離子體光催化劑，對催化劑的微結構和光學性質進行了表徵分析。將制備的Ag/Ag X應用於光催化凈化空氣中NO，Ag/Ag Cl因具有更強的等離子體效應和更高的電荷分離效率而表現出較高的光催化性能。運用原位紅外光譜動態監測了Ag/Ag Cl光催化凈化NO的反應過程，從分子層面揭示了Ag/Ag Cl等離子體可見光催化氧化NO的反應機理。本研究為貴金屬基等離子體光催化劑的作用機理及空氣凈化應用提供了新的認識。
Photocatalysis technology could utilize solar energy for pollutants degradation and water splitting, displaying great potential in environmetnal remidiation and clean enerfy development. Significant progresses have been made on promoting photocatalysis efficiency and extending light absorption range. Specific semiconductors and plasmonic metals can behave photocatalysts. Recently, the plasmonic photocatalysis with Ag/AgX（X=Cl,Br,I） has been received increasing research interests. The preparation and application of Ag/AgX plasmonic photocatalysts have extensively explored. However, the Ag/AgX plasmonic photocatalysts were mainly applied in water splitting and degradation of aquous pollutants. The application of Ag/AgX in air purification has been rarely reported. Also, the mechanism of photocatalytic NO purification with Ag/AgX has never been revealed. Noble metal nanoparticles showed obvious characteristic absorption in the visible light region due to surface plasmon resonance effect. Under the induction of visible light, silver/silver halide（Ag/AgX,X=Cl,Br,I） compounds shows excellent photocatalytic performance in the purification of pollutants. This research adopted the method of precipitation at room temperature to prepare Ag/AgX plasmonic photocatalyst. The formation of Ag metal on the AgX surface can be ascribed to the natural light illumination. The microstructure and optical properties of the as-prepared catalysts were characterized with XRD, SEM, UV-Vis DRS and PL techniques. The prepared Ag/AgX was applied in photocatalytic purification of ppb-level NO in the air. NO is one of the typical indoor and outdoor air pollutants. The results indicataed that the Ag/AgC l showed higher visible light photocatalytic performance due to the strong surface plasmon resonance absorption and the high charge separation efficiency in camparison with Ag/AgB r and Ag/AgI. The process of photocatalytic NO purification with Ag/AgC l was dynamically monitored with in situ FT-IR equipped with an in situ diffuse-reflectance cell. The time-dependent evolution of IR peaks have been identified.The plasmonic visible light photocatalytic NO oxidation reaction mechanism with Ag/AgC l was revealed at molecular level. The reaciton mechanism can be described as Ag⁺visible light→e⁻⁺h⁺, e⁻⁺O₂→·O₂, h⁺⁺AgCl→Cl₀⁺Ag⁺, ·O₂⁺NO→NO⁻₃, Cl₀⁺NO→Cl⁻⁺NO⁻₃ and Cl⁻⁺Ag⁺→AgCl. The present work could provide a new perspective in the undestanding of the mechanism of noble metal based function plasmonic photocatalyst and air purification application. Copyright © 2016 《中國科學》雜誌社.