Fabrication And Application Of Silver Orthophosphate-graphene Photocatalytic Composite

Since it was reported by Ye’s group, silver orthophosphate (Ag3PO4), a highlyvisible light response photocatalyst, has been intensively investigated. HoweverAg3PO4is unstable during the process of photocatalysis due to the slight dissolvingcapacity in aqueous solution. Because the conduction band potential of Ag3PO4(0.45eV vs NHE) is more positive than that of the hydrogen potential, thetransformation of Ag+into Ag usually takes place, which results in the photocorrosionof Ag3PO4in the absence of electron acceptors. These factors limit the utmost use ofAg3PO4in energy and environment field.Graphene, a monolayer of hexagonally arrayed sp2-hybridized carbon atoms, hasattracted tremendous research interesting from various fields because of its largespecific surface area and exceptional electrical, mechanical, thermal and opticalproperties.Considering that Ag3PO4can be excited under visible light and construction ofcomposite materials can enhance photocatalytic activities and stabilities. Ag3PO4/GOcomposite and Ag3PO4/RGO composite were synthesized by facile methods in thisthesis. Listed below are the results: Specific contents are as follow:(1) One-step synthesis of Ag3PO4/GO composite has been put forward. Themorphology and photo-electrochemical property of our samples have been carefullycharacterized by Scanning Electron Microscope, X-ray Diffraction Pattern, FourierTransform Infrared Spectra, Raman Spectroscopy and Diffuse ReflectanceSpectrophotometry. The photocatalytic property and the influence of graphene oxide(GO) have also been test. The results prove that the content of GO can influence thephotocatalytic performance of the materials, among them, Ag3PO4/GO-1.5wt.%displayed the highest photocatalytic activities. The apparent reaction rate constant (k)of photocatalytic removal of Rhodamine B over Ag3PO4/GO-1.5wt.%was0.7249min-1, nearly3.8times than0.1918min-1over bare Ag3PO4.(2) Here in, as an initial attempt, Ag3PO4/RGO composite has been synthesizedby an in suit chemical deposition method without adding any organic solution or usinghigh temperature. The physical and chemical properties of the as-prepared sampleswere characterized by various techniques. The photocatalytic activities and stabilitywere evaluated by degradation of organic dye under visible light irradiation. Therelationship between structure and catalytic performance was also investigate. The encapsulation of Ag3PO4with RGO sheets effectively transferred the photoinducedelectrons to inhibit Ag3PO4from photocorrosion, which contribute to the enhancedphotocatalytic activity and structural stability of the composite photocatalyst. Inaddition, the quenching effects of different scavengers proved that both holes and O2active species played major roles in the photodegradation process. A possiblephotocatalytic mechanism of the Ag3PO4/RGO composite was proposed as well.