| In addition to the continuously improvement in the quality of life,the rapid development of technology and industry has also lead to serious water pollution all around the world.How to solve this environmental problem has already been considered as one of the most urgent tasks in this century.As an environmental-friendly technology for remediation of organic pollutants in water,semiconductor photocatalyst TiO2 has attracted considerable attention.However,the widegap(3.2 eV)of TiO2 limits its optical absorption in the UV range,hence the application of TiO2 for photodegradation of organic pollutants in water under visible light is extremely impractical.In order to utilize the solar energy in the visible range,various novel visible-light-driven photocatalysts have been developed.Among these photocatalyts,Bi-based compounds have caused a lot of attention due to its suitable gap width,high electron mobility and large absorption coefficient for visible light absorption.In this paper,bismuth-based oxyhalide is used as a substrate for photocatalyst and modified to achieve the purpose of improving its photocatalytic performance.Through a series of testing methods,the mechanism explanation of the improvement of photocatalytic performance is proposed.The main content can be divided into the following three parts:(1)Bi24O31Cl10 photocatalysts were prepared via a hydrothermal method and then modified by Pt nanoparticles(NPs)by a facile deposition procedure.The 1.0 wt%Pt/Bi24O31Cl10 photocatalyst showed highest photocatalytic activity for degradation of methyl orange(MO)under visible light(300 W Xe lamp),and the photocatalytic degradation efficiency was improved for about 2.2 times as compared to that of pure Bi24O31Cl10.The composite photocatalysts were characterized by X-ray diffraction,transmission electronic microscope,X-ray photoelectron spectroscopy,UV-vis diffusion reflectance spectroscopy,photoluminescence spectra,and electron spin resonance.The enhancement of the photocatalytic performance of the Pt loaded Bi24O31Cl10 nanosheets is mainly due to the efficient interfacial charge transfer in the composite sample.(2)A novel plasmonic photocatalysts of Ag-AgI/Bi3O4Cl was successfully synthesized via a mild wet-chemical process.The 30 wt%Ag-AgI/Bi3O4Cl photocatalyst showed the highest photocatalytic activity for degradation of methyl orange(MO)under visible light(5 W LED lamp),which represents a 3.2 and 7.4 times enhancement in the photocatalytic degradation efficiency as compared to pure Bi304Cl and Ag-AgI,respectively.The surface plasm on resonance effect of Ag nanoparticles was detected by the UV-vis diffusion reflectance spectroscopy and surface photovoltage measurement,finding that the this effect of Ag extends the absorption and photo response range in the Ag-AgI/Bi3O4Cl composite photocatalyst.Based on the analysis of electron spin resonance,linear sweeping voltammetry characterization results,three electron transfer processes were proposed(3)Bi304Cl and Bi3O4Cl-OV with oxygen vacancies were successfully synthesized and detected by the UV-visible diffuse reflectance spectra(DRS),X-ray photoelectron spectrometer(XPS)and Kelvin probes to explore the impact of the oxygen vacancies on the energy band structure.It is proposed that the defect states will shorten the forbidden band,close the distance between the Fermi level and the conduction band,and reduce the work function.All these effects provide a reasonable explanation for the performance improvement of Bi3O4Cl-OV.At the same time,Bi3O4Cl-OV was further modified by loading with metal halide AgBr and the photocatalytic degradation efficiency was improved for about 11.2 times as compared to that of pure Bi3O4Cl. |
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