In-situ Synthesis And Photocatalytic Properties Of BiOCl Thin Films

BiOCl diaplays good photocatalytic activity in dye degradation and has been considered to be a competitive and promising photocatalytic material in the21 st century,due to its unique microstructure and indirect transition mode.However,the performance of BiOCl powder photocatalyst is limited by the solid-liquid separation defect,such as easy to aggregate and sediment in solution,difficult to separation and recycle,the high operating cost.Therefore,the immobilization of BiOCl photocatalyst has become the research focus of photocatalysis field.The in-situ synthesis is a method for preparing BiOCl film directly on the surface of Bi plate.The obtained film has a good compatibility with substrate material and is closely combined with Bi plate in the chemical bonding way,leading to a good adhesion to the Bi plate without falling off easily.Moreover,this method has the following advantage: mild reaction conditions,simple operation process and environmental friendly.Hence,the immobilization of BiOCl photocatalyst by in-situ synthesis has been intensively studied.In this paper,BiOCl thin films photocatalysts with different morphologies were directly synthesized on Bi plate by in-situ methods?redox methods andelectrochemical method?.The formation mechanisms,physical and chemical properties and photocatalytic performance were investigated.It is expected to have some reference and guidance for the future application of this photocatalyst and the development of immobilization technology.The main research contents are listed as follows:Part 1.Fabrication of BiOCl thin film by Na Cl O redox method and its photocatalytic propertiesSodium hypochloride?Na Cl O?was used as Cl source to synthesize tetragonal phase BiOCl thin film on bulk Bi plate.The structure,morphology and photocatalytic activity of the as-prepared film were investigated.It was indicated that the surface of BiOCl thin film was composed of microspheres like knitting yarn,which were assembled by ultrathin sheets.The BiOCl thin film performed efficient photocatalytic activity and good photochemical stability towards photodegradation of Rh B under simulated solar light,the decomposition efficiency of Rh B was 98.2% in 210 min under simulated solar light irradiation,the photocatalytic degradation efficiency still remain 91.6% after being used four times.The formation mechanism of BiOCl thin film exhibited that,the Clions were slow-released through redox reaction of Na Cl O and EG,just the slow-released Cl-ions played important role in the formation of BiOCl thin film on Bi plate.Part 2.Fabrication of BiOCl thin film on bulk Bi plate via FeCl₃ redox method and its photocatalytic propertiesFeCl₃ was used as oxidant and Cl source to grow BiOCl thin film on bulk Bi plate by in-situ synthesis at room temperature.The structure,morphology and photocatalytic activity of the as-prepared film were investigated.The BiOCl thin film was found that the as-prepared film could be perfectly indexed as tetragonal phase of BiOCl,which had a compact and uniform surface.The BiOCl thin film was 0.1-3 ?m sheet-structure observed from the high-magnification SEM image.It displayed excellent photocatalytic activity,the photocatalytic degradation efficiency could reach 97.5% under 180 min simulated solar light irradiation,and it had great stability,the photocatalytic degradation efficiency still remained above 96% after being used five times.The degradation mechanism of Rh B by BiOCl thin film was studied,which indicated that ·O2-and h+ were main reactive active species,and the effect of ·O2-was larger.Part 3.The preparation of BiOCl film via electrochemical method and its photocatalytic activitiesBiOCl thin film was prepared in the sodium hypochloride?Na Cl O?via one-step electrochemical method at room temperature,the bulk Bi plate as anode and graphite sheet as cathode.The structure,morphology and photocatalytic activity of the as-prepared film were investigated.The BiOCl-0thin film was uniform with nanosheet structure.The parameters of the preparation process were optimized,the optimization conditions were when the concentration of Na Cl O was 0.095 mol,electrolytic current was 0.05 A,the dosage of EDTA was 2 mmol and original p H value?p H=7.5?.At the same time,the BiOCl-0 thin film expressed excellent photocatalytic activity.The efficiencies of Sulfamethoxazole was 89.8% in 150 min under simulated solar light,the photocatalytic degradation efficiency still remained above 82% after being used five times.