Study On The Preparation And Photocatalytic Activity Of BiOI Composite Materials

With the industrial development and population growth,global environmental pollution and energy supply demand are increasing.Large amounts of toxic substances such as industrial wastewater,synthetic dyes and heavy metals have caused the global water pollution increasingly worse.The removal of organic pollutants in wastewater has attracted more and more attention,and various biological,physical and chemical treatment technologies are used to convert or remove organic pollutants in water.Semiconductor photocatalysis technology has wide application prospect,especially in environment and energy.More and more attention has been paid to BiOI semiconductor materials.In this thesis,the preparation and photocatalytic properties of ZnO/BiOI and BiOI/MoS2 composites were studied.Flaky and flower-shaped ZnO were prepared by controlling the reaction time and the amount of surfactant using hydrothermal method.The obtained materials were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),nitrogen absorption desorption,UV-vis absorption spectra and Mott-Schottky(M-S)analysis methods.The effects of reaction time,calcination temperature,and the amount of surfactant were investigated on the photocatalytic properties of ZnO.The results show that the reaction time,calcination temperature and the amount of surfactant all affect the morphology and properties of ZnO.In the process of simulated solar photocatalytic degradation reaction of methyl orange,ZnO-6 material which is obtained under the condition of holding time 4h,calcining temperature 500? and surfactant dosage 0.25 g has the highest photocatalytic degradation efficiency.Methyl orange(MO)solution can be completely degraded in 80 min.Meanwhile,the ZnO-6 materials showed excellent photocatalytic stability.The degradation rates for MO were 99%in all the five times degradation cycles.ZnO/BiOI composites were prepared by mechanical grinding method.Scanning electron microscopy(SEM)was used to characterize its morphology,and the photocatalytic degradation properties of ZnO/BiOI composite were also investigated under visible light.The results show that the photocatalytic activity of the composite is significantly improved compared with that of pristine ZnO material.However,the photocatalytic properties of ZnO/BiOI composite was poorer than that of pristine BiOI material which may be attributed to the wide band gap of ZnO.ZnO/BiOI thin-film material were prepared by acid soaking method and chemical adsorption method.The structure of the photocatalyst was characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),UV-vis absorption spectra and M-S curves,and the photocatalytic properties of visible light were investigated.The results show that the combination of ZnO thin-film material and BiOI material significantly improved the photocatalytic activity of single material.The degradation rate of ZnO/BiOI composite on methyl orange solution is up to 99%in 180 min under visible light.The ZnO/BiOI composite structure is beneficial to the separating of photogenerated electrons and hole pair,reducing its recombination probability,and thus having higher photocatalytic efficiency.BiOI/MoS2 materials were prepared by solvothermal method,the structure of the photocatalyst was characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),nitrogen absorption desorption curves,PL spectra,photocurrent curves,UV-vis absorption spectra and M-S curves.The results show that the photocatalytic activity of BiOI/MoS2 increases with the increase of MoS2 contents first,then it decreases when MoS2 content is over 0.5%.The degradation efficiency of methyl orange could achieve 95%within 90 min in the presence of BiOI-0.5%MoS2,which is about two times higher than that of pristine BiOI nanostructures.The obviously improved photocatalytic performance of BiOI/MoS2 could be mainly attributed to the significantly enhanced separation efficiency of photogenerated charge carriers.However,too much MoS2 loading on the surface of BiOI will prevent light from reaching surface of BiOI and limit the efficiency of charge separation.Based on active specie trapping experiments,holes(h+)was proved to be the main reactive species in the degradation of MO.