Synthesis And Photocatalytic Performance Of Bismuth Oxyiodide-based Heterojuntion Photocatalysts

As a widely used synthetic estrogen,EE2 has the potential to elicit negative effects on the endocrine systems,reproductive system and nervous system of humans and wildlife.EE2 has been detected in wastewater treatment plants,ground water and even drinking water,implying that the existence of EE2 in water would bring serious threats to human beings and animals.Therefore,it's very urgent and essential for us to explore an effective method to degrade EE2 in water.Photocatalysis method has been proven to be a promising technology for water purification because of its high efficiency,low cost and low toxicity.In this paper,CdS/BiOI and BiOI/Bi₅O₇I photocatalysts were synthesized via the solvothermal–chemical bath deposition method and precipitation method,respectively.The physical and chemical properties of photocatalysts were characterized based on XRD,SEM,TEM,EDS,XPS,BET,UV-vis DRS and PL techniques.Photocatalatytic activity of the as-prepared CdS/BiOI and BiOI/Bi₅O₇I photocatalysts were investigated through the degradation of EE2 under visible light irradiation,and the photocatalytic mechanism of the degradation process was thoroughly elucidated.The details are as follows:1.A novel CdS/BiOI photocatalyst has been prepared via the solvothermal–chemical bath deposition method.According to the characteristic analysis and the experimental results,the optimal preparation conditions were established to be that the hydrothermal temperature was 140?,the hydrothermal time was 12 h,the molar ratio of Cd/Bi was 3:1,the dosage of NH₄Cl was 0.04 g,the dosage of NH₃·H₂ was 2 mL and the water bath temperature was50?.The photocatalytic performance of CdS/BiOI photocatalyst was evaluated by the photocatalytic degradation of 3 mg/L EE2 under visible light irradiation.When the photocatalyst dosage was 0.3 g/L and the pH value of EE2 was 5.8,98.4%of EE2 was degraded over CdS/BiOI potocatalyst after 8 min of visible light irradiation,and 100.0%of EE2 was degraded after 20 min of visible light irradiation.The photocatalytic reaction rate of CdS/BiOI was 7.18 and 6.39 times higher than that of BiOI and CdS,respectively.On the basis of the experimental results and the theoretical calculation,a Z-scheme charge separation mechanism was proposed.2.The BiOI/Bi₅O₇I photocatalyst has been synthesized via the deposition method.According to the characteristic analysis and the experimental results,the optimal preparation conditions were established to be that the mass ratio of BiOI was 60%,the kind of alkali was NaOH and pH value was 11.The photocatalytic performance of BiOI/Bi₅O₇I photocatalyst was evaluated by the photocatalytic degradation of 3 mg/L EE2 under visible light irradiation.When the photocatalyst dosage was 0.3 g/L and the pH value of EE2 was5.8,97.9%of EE2 was degraded after 16 min of visible light irradiation.The photocatalytic reaction rate of BiOI/Bi₅O₇I was 3.74 and 5.76 times higher than that of BiOI and Bi₅O₇I,respectively.The BiOI/Bi₅O₇I photocatalyst has good photocatalytic activity and stability.The formation of p-n junction between the p-type BiOI and n-type Bi₅O₇I greatly promoted the separation and migration of electron-hole pairs,which could help enhance the photocatalytic activity of BiOI/Bi₅O₇I photocatalyst.