Synthesis And Visible Light Catalysis Ag₂WO₄ Based Composite Catalyst

Semiconductor photocatalyst gets widespread attention since there is a huge potential application in solving the current environmental problems. Ti O2 is the most widely studied and used photocatalyst, but the band gap of Ti O2 is 3.2 e V, can only be excited by UV light, can not actually large-scale use of solar light. So it is very urgent to develop a new visible light catalytic material which can be excited by visible light.Silver based photocatalysts have attracted much attention because of the physical and chemical properties and potential applications, it has been proved efficient visible-driven dynamic. Silver tungstate(Ag2WO4) has been reported as a photocatalytic material, especially the metastable beta-Ag2WO4 which has highly efficient visible light catalytic activity, because it is not stable enough, it is necessary to explore an effective way to maintain the metastable structure.In this paper, the effects of the introduction of Bi OI and g-C3N4 on the morphology and visible photocatalytic activity of Ag2WO4 were studied, and two kinds of highly efficient visible light catalysts were prepared by the synthesis of Bi OI/Ag2WO4 composite and g-C3N4/Ag2WO4 composite. It mainly includes the following two parts:The first part: Preparation of Bi OI powder by solvent thermal method ethylene glycol as solvent, then preparation of Ag2WO4/Bi OI composite photocatalyst with different proportions by chemical precipitation method at room temperature. Structural properties of the composite samples were characterized by means of XRD、FT-IR、XPS、TEM、N2 adsorption desorption、UV-vis、PL. The results indicated that the morphology of composite changed from primary rod-like particle to globular nanoparticle, which resulted in its phase changing from á-type to a-type.The photocatalytic activity of the catalyst was tested by the degradation of the pollutant dye model Rhodamine B(Rh B).Due to Bi OI had excellent response and absorption capacity for visible light, and the composite enhanced the photogenerated electron-hole pair separation efficiency.Therefore, Ag2WO4/Bi OI composite photocatalyst had a higher photocatalytic activity under visible light. The reaction activity of the composite was still higher after five cycles, which proved that the composite material had good stability.The second part: Carbon nitride(g-C3N4) powder was obtained by calcination at550 °C to maintain 4 h, then preparation of g-C3N4/Ag2WO4 composite photocatalyst with different proportions by chemical precipitation method at room temperature.Structural properties of the composite samples were characterized by means of XRD、FT-IR、XPS、TEM、N2 adsorption desorption、UV-vis 、PL. Exploring the best proportion by the photocatalytic degradation of dye model(Rh B).The results indicated that the morphology of composite changed from primary rod-like particle to globular nanoparticle, which resulted in its phase changing from á-type to a-type. Due to their synergistic effects and differences in the band structure, the effective separation of the photogenerated electron-hole pair has been obtained. The visible light response and photocatalytic activity of the composite was higher compared with the pure phase g-C3N4 and Ag2WO4. The composite was proved to have good stability by cyclic experiment. The photocatalytic degradation mechanism was presented through the quenching experiment of the intermediate.