Study On The Bi-based Composite Photocatalysts:Synthesis,Performance And Mechanism Research

Increasing demands of energy is accompanied by dramatic economic development,energy shortage and environmental pollution are become more and more serious.The development of human society depends on the appearance and using of clean energy,so seeking renewable clean energy sources become a trend.These alternative sources of energy sources must be environmental friendly,inexpensive and must be renewable.Renewable energy sources mainly include sunlight,wind,water,geothermal heat,hydrogen etc.Among various renewable energy options,solar energy is the most abundant,environmental,safe and pollution-free energy source in the nature.However,production costs and environmental costs are high of solar panels by using photovoltaic conversion in the past.In recent years,photocatalytic technology as a kind of new technology,plays a vital role in the fight against global environmental pollution and energy shortage.Preparing semiconductor materials with high photocatalytic activities are the core of the photocatalytic technology.Therefore,how to design a visible-light-active photocatalyst is critical for efficient solar energy utilization.Bi₂MoO₆ and BiOBr,a novel visible light response semiconductor photocatalyst,have attracted much attention due to they have open layered structure,moderate band gap and high catalytic capacity etc,and a series of research progress has been acquired.How to further improve the visible catalytic activities of Bi₂MoO₆ and BiOBr has been a problem that needs to be solved at the present stage.In this paper,a simple hydrothermal method was adopted to produce efficient SnS₂/Bi₂MoO₆,SnO₂/BiOBr and SnO₂/Bi₂MoO₆ composite photocatalysts by introducing a small amount of SnS₂ or SnO₂.The crystal morphology,size,microstructure,optical properties,active species of photocatalysts were measured by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,Fourier transform infrared spectroscopy?FT-IR?,fluorescence spectroscopy?PL?,Uv-vis diffuse reflection spectroscopy?UV-Vis DRS?,electron spin resonance?ESR?and other modern research techniques characterization testing,then put forward the possible photocatalytic mechanism.The photocatalytic activities of the prepared catalysts were evaluated by degrading rhodamine B?RhB?,crystal violet?CV?,ciprofloxacin?CIP?and triclosan?TCS?by 5 W LED lamps.The dynamics of the reaction was discussed.In this paper,the main research contents and conclusions are as follows:?1?Through a facile hydrothermal method,SnS₂/Bi₂MoO₆ composites were successfully prepared by the raw materials of SnCl₄.5H₂O,Bi?NO₃?₃.5H₂O and?NH₄?₆Mo₇O₂₄·4H₂O.Crystal violet and ciprofloxacin were used as the degradation model to evaluate the photocatalytic degradation of organic pollutants under simulated sunlight.The experimental results showed that the photocatalytic activities were significantiy improved of SnS₂/Bi₂MoO₆ composites,especially 5 wt%SnS₂/Bi₂MoO₆.Furthermore,it was speculated that SnS₂/Bi₂MoO₆ heterojunction photocatalyst might belong to Z-scheme photocatalytic mechanism by capturing experiments and ESR analysis in photocatalytic process.?2?The Sn O₂/BiOBr composites were firstly synthesized by one-step hydrothermal method, and the results of XRD,SEM,TEM,XPS and other characterization methods showed that SnO₂nanoparticles close loaded on Bi OBr nanofilms.Rhodamine B,crystal violet,and triclosan were used as the degradation model to evaluate the photocatalytic degradation of organic pollutants.The results showed that the suitable quantity of SnO₂ in composites showed excellent photocatalytic activities,proved that the p-n heterojunction promotesd the separation of photoinduced electron-hole pairs,and then improved the photocatalytic efficiency.The capture experimentS and ESR analysis showed that the main active species in the photocatalytic process were superoxide free radicals(·O^2-)and hydroxyl radical?·OH?.In addition,SnO₂/BiOBr composites exhibited good recycling stability by cyclic experiments.?3?In this section experiment,SnO₂/Bi₂MoO₆ composite photocatalysts were synthesized by simple one-step hydrothermal method.The properties of different mass ratio of SnO₂/Bi₂MoO₆ composites were analyzed through the degradation of crystal violet solution,proved that 7 wt%SnO₂/Bi₂MoO₆photocatalyst had the best catalytic activity,it was attributed to the effects of low recombination rate of electron–hole pairs in the heterogeneous interface between the two semiconductors.Furthermore,a series of characterizations of the photocatalysts were made to analyze the morphology,microstructure and optical properties.