Preparation And Photocatalytic Of Bi₄Ti₃O₁₂ By Molten Salt Method

Bi₄Ti₃O₁₂2 is a layered perovskite oxide with a unique crystal structure and electronic structure.It is a promising photocatalyst with a narrow band gap and can theoretically respond in the visible region.Molten salt synthesis method has been widely used in the synthesis of ceramic powders because of its advantage of liquid reaction medium.In this thesis,Based on the molten salt method,the effects of reaction temperature and salt ratio on the morphology and structure of Bi₄Ti₃O₁₂powders were discussed,the photocatalytic performance of Bi₄Ti₃O₁₂2 powders was evaluated by the degradation of Rhodamine B under visible light??>420 nm?.Moreover,our research is focused on the preparation and photocatalytic performance of Bi₄Ti₃O₁₂/g-C₃N₄;Ag/Bi₄Ti₃O₁₂;Pt/Bi₄Ti₃O₁₂2 and AgPt/Bi₄Ti₃O₁₂2 composite.The results indicate that:?1?Phase pure Bi₄Ti₃O₁₂2 can be obtained by molten salt method at 800°C.Bi₄Ti₃O₁₂2 synthesized by molten salt method has anisotropy and grows along ab plane orientation.The Bi₄Ti₃O₁₂2 prepared by the molten salt method has a sheet structure,and its size increases with the increase of the reaction temperature.The grain growth during the molten salt process can be explained by the Ostwald ripening mechanism;The photocatalytic performance of Bi₄Ti₃O₁₂2 showed that,compared with Bi₄Ti₃O₁₂synthesized by conventional solid reaction method,plate-like Bi₄Ti₃O₁₂2 powders prepared by present method had better photocatalytic performance.The photocatalytic degradation for RhB degradation of the former is about 8.2 times as that of the granular Bi₄Ti₃O₁₂2 synthesisde by traditional solid state reaction method,which can be ascribed to that Bi₄Ti₃O₁₂2 powders prepared by molten salt method has more active sites and can effectively separate photogenerated electrons and holes.?2?Bi₃Ti₄O₁₂/g-C₃N₄ composite photocatalysts were prepared by a mechanical mixing/heat treatment-method.The structure and morphology of as-prepared Bi₃Ti₄O₁₂/g-C₃N₄ composite photocatalysts were characterized.The results showed that heterojunction structure is formed in the Bi₄Ti₃O₁₂/g-C₃N₄,thus decreased the band gap of Bi₄Ti₃O₁₂,red-shifted the absorption band edge,and enhanced the absorption of visible light.The photocatalytic activity for the degradation of RhB solution showed that,compared with the phase pure Bi₄Ti₃O₁₂,Bi₃Ti₄O₁₂/g-C₃N₄composite photocatalysts had better photocatalytic performance.It is found that Bi₄Ti₃O₁₂/g-C₃N₄?20wt%?exhibited the best photocatalytic activity.The photocatalytic degradation for RhB of Bi₃Ti₄O₁₂/g-C₃N₄ composite photocatalysts is about 4 times as that of Bi₄Ti₃O₁₂.The higher photocatalytic activity can be ascribed to the formation of a heterojunction between Bi₄Ti₃O₁₂2 and g-C₃N₄,which markedly suppressed the recombination of photogenerated electron-hole pairs.The analysis of the radical scavengers experiment results confirmed that h⁺and·O^2-were the primary reactive species for the photocatalysis process.?3?The Bi₄Ti₃O₁₂2 powders prepared by molten salt method were used as raw materials,AgNO₃ and H₂PtCl.6H₂O were used as silver source and platinum source.Ag/Bi₄Ti₃O₁₂,Pt/Bi₄Ti₃O₁₂2 and AgPt/Bi₄Ti₃O₁₂2 composite photocatalysts were successfully prepared by photoreduction method.SEM results show that Bi₄Ti₃O₁₂still maintains the sheet structure after loading Ag or Pt nanoparticles;the photocatalytic degradation of rhodamine B results show that the loading of Ag or Pt nanoparticles can improve the catalytic performance of Bi₄Ti₃O₁₂,when the loading amount of Ag nanoparticles was 0.1wt%,the Ag/Bi₄Ti₃O₁₂2 composite photocatalyst had the best catalytic performance,and the photocatalytic degradation for RhB degradation is about 1.8 times as that of Bi₄Ti₃O₁₂.Under the same loading,the photocatalytic degradation for RhB degradation of Pt/Bi₃Ti₄O₁₂2 composite photocatalysts is about 2.1 times as that of Bi₄Ti₃O₁₂;the performance of the catalyst after loading bimetallic nanoparticles is better than that of monometallic nanoparticles;when m?Ag?:m?Pt?=7:3,the apparent reaction rate of AgPt/Bi₄Ti₃O₁₂2 supported photocatalyst is 3.7 times as that of single-phase Bi₄Ti₃O_12....