Synthesis And Photocatalytic Properties Of Ag/WO₃-based Composites Based On Plasma Resonance Effect

Photocatalytic materials based on metal oxide semiconductors and their composites have been regarded as the research hotspots to degrade organic pollutants.Tungsten trioxide(WO3),as one of the semiconductor materials,has gained increasing research interest for its utilization in development of photocatalyst due to its relatively narrow band-gap energy,outstanding stable physicochemical properties and nontoxicity.Meanwhile,noble metal doping can not only enhance light absorption of the material itself duo to surface plasma resonance effect of noble metal,but also effectively restrain recombination of electron-hole by introduction of metallic Ag to build Z-scheme structure.In this dissertation,preparation process,phase structure,catalytic activity and mechanism are discussed for the material development and practical application.The main contents are as follows:(1)WO3 nano-blocks are synthesized by hydrothermal method,and the Ag/AgCl/WO3 composited photocatalysts with different contents of Ag/AgCl nanoparticles are prepared through precipitation and photoreduction method in geothermal water,wherein the geothermal water served as the chlorine source and possible surfactant.It is found that the as-prepared 50 wt%Ag/AgCl/WO3 photocatalyst showed the highest photocatalytic 4-ABA efficiency with 25.12 and 3.53 times higher than those of pure WO3 and Ag/AgCl,respectively.(2)Ag/?-Ag2WO4/WO3 composites are prepared by depositing ?-Ag2WO4 particles on WO3 nano-blocks through the reaction between Ag+ and WO42-followed by photo-reduction.The composite materials show good degradation activity to anionic and cationic dyes.The key factors in the improvement of catalytic performance are the enhancement of light absorption result of surface plasma resonance effect and effective separation of electron hole pairs.(3)Ag/Ag3PO4/WO3 heterostructures are fabricated using the above-mentioned similar methods.To explore more deeply about the photocatalytic activity of as-prepared materials under neutral and strongly acidic/alkaline conditions,we have investigated their photocatalytic rhodamine B efficiency at different pH value that was controlled by adding HNO3 or NaOH aqueous solution.It is found that asprepared AAPW photocatalysts show enhanced photocatalytic RhB efficiency under neutral and even strongly acidic/alkaline environment.The process of charge carrier separation and transfer in nanocomposites and Z-scheme mechanism for RhB degradation are described in sufficient detail based on systematical characterizations and measurements.The silver particles introduced to build Z-scheme structure should contribute to more efficient charge separation,resulting in enhanced photocurrent response and photocatalytic activity.