Controllable Construction Of High-efficiency Bi-based Heterostructure As Visible-light Catalytic Materials

Because of the global energy demand and environmental pollution problems,photocatalytic technology for water decontamination has attracted great attention in the past years.Semiconductor photocatalysts with different morphologies,microstructures and excellent performances have been synthesized.The bismuth-based compound possess narrow band gap,unique layered structure and high visible light photocatalytic activity.However,pure Bi-based photocatalysts have the disadvantages of easy recombination of photogenerated carriers,which limits its application.Therefore,construction of a heterostructure to prolong the life of electron-hole pairs is a very important approach to endow it with excellent photodegradation performances.In this paper,the photocatalytic performance is improved by the method of synthesizing the Bi-based photocatalyst heterostructure.On the one hand,one-pot is used to synthesize BSO heterostructures with the same component but different crystal structures to form a proper band gap.On the other hand,a novel Ag6Si2O7/BiOBr photocatalyst with heterojunction structure is simply synthesized by the hydrothermal and co-precipitation method.The photocatalytic properties of these two heterostructures are studied.The detail content is as followed:(1)Bismuth silicate(BSO)heterostructures:Bismuth silicate(BSO)heterostructures are synthesized using a one-pot hydrothermal approach without adding any other inorganic components.The amount of CTAB used in the experiment plays two roles.on one hand CTAB acts as Br source to control chemical composition,and the other hand CTAB acts as surfactant to adjust the surface morphology.Two BSO heterostructures are synthesized:Bi2SiO5 nanoparticles are anchored on Bi12SiO20 or Bi4Si3O12 sheets to form rod-like and flower-like heterostructures,respectively,exhibiting greatly improved visible light irradiation absorption and dye adsorption.Thanks to the two heterostructures and clean surface,the optimized BSO material exhibits a highly active photocatalytic performance with a remarkable cycling stability.(2)Ag6Si207/BiOBr heterostructures:A novel Ag6Si2O7/BiOBr photocatalyst with heterojunction structure is simply synthesized by the hydrothermal and co-precipitation method for the first time.The effect of loading amounts of Ag6Si2O7 nanoparticles anchored on BiOBr nanoflakes on the photocatalytic activity in visible light regions is totally investigated using methylene blue(MB)and methyl orange(MO)as degradation models.To clarify the photodegradation of Ag6Si2O7/BiOBr,morphology,crystal structure,absorption performance,bandgap energy and several factors are carried out.The formed AB-20(the mole ratio of Ag6Si2O7/BiOBr=2:10)has the best photocatalysis ability among other ratios and the pure materials.At the same time,the catalyst is used to explore the degradation performance of the mixed organic pollutants.Due to the enhanced adsorption and the competition between the catalysts,AB-20 exhibits a significant rate increase in MO degradation and a slower rate in MB degradation.