Preparation And Photocatalytic Performance Of Bi₂SiO₅ And Its Composite Photocatalyst

In recent years,bismuth-based semiconductor have been widely investigated due to their excellent photocatalytic performance,non-toxicity,and stable chemical properties.However,wide-band gap materials such as Bi₂SiO₅cannot respond to visible light and have low quantum efficiency which limit its further application in practice.Therefore,how to modify Bi₂SiO₅to widen its spectral response range has important practical significance.Construction of heterojunction is one of effective ways to modify semiconductor catalysts.In view of this,in this paper we constructed Bi₂SiO₅-based heterostructure to improve its photocatalytic activity.First of all,Bi₂SiO₅/Bi₄Si₃O₁₂ composite catalysts were synthesized by matching the energy gap between different crystalline forms of bismuth silicate.Then,different materials were used to match energy gap with Bi₂SiO₅to construct heterostructures.At the same time,by dye sensitization effect of Rhodamine B and the surface plasmon resonance effect of Ag nanoparticle,the photocatalytic performance of Bi₂SiO₅can be improved synergistically.Main research works and results are as follows:（1）Bi₂SiO₅/Bi₄Si₃O₁₂ composite catalysts were synthesized by one-step hydrothermal method.Heterojunction formed between Bi₂SiO₅and Bi₄Si₃O₁₂facilitated migration and separation of photo-generated carriers.Compared to pure Bi₂SiO₅,the composite catalysts had superior photocatalytic activity.Among them,BSO-0.5 sample showed the best photocatalytic performance.CTAB not only acted as a surfactant to adjust the morphology of the composite catalysts,but also acted as Br source in the reaction to effect the phase composition.Results of free radical capture experiments showed that h⁺and·O^2-were the main active species in the photocatalytic process of BSO-0.5 sample.（2）AgBr/Bi₂SiO₅ catalysts with a Z-Scheme structure were prepared by combination of hydrothermal method and precipitation method.Among them,S-1.5 sample had the best photocatalytic activity under visible light.Pure Bi₂SiO₅had a weak photocurrent response while AgBr/Bi₂SiO₅composite catalysts had a strong photocurrent response.Results of free radical capture experiments show that·O^2-was the main active specie in the photocatalytic process of AgBr/Bi₂SiO₅composite catalyst,and·O^2-was the main oxidizing substance in the deethylation reaction of Rhodamine B.The electrons generated by self-sensitized Rhodamine B transferred to the conduction band of Bi₂SiO₅,and then recombined with the valence band holes of AgBr via the ohmic contact surface.The formation of the Z-Scheme structure promoted the separation and transmission of carriers and improved the photocatalytic activity of the composites under visible light.（3）Ag/AgCl/Bi₂SiO₅ composite catalysts with a ternary heterojunction were constructed by the combination deposition method and photoreduction method.The composite had excellent photocatalytic activity with dye universality.Among them,S3 sample showed the best photocatalytic activity under visible light irradiation.Results of free radical capture experiments showed that h⁺was the most important active species in the photocatalytic process.The composite catalysts showed excellent photocatalytic activity in the visible light region due to the SPR effect of Ag nanoparticles.The ternary heterostructure improved the separation efficiency of photogenerated electron-hole pairs.