Synthesis Of Bi₂O₃/C₃N₄por Composite Photocatalysts And Study Of Self-driven Photo-Fenton Mechanism

Photocatalytic technology can convert solar energy into chemical energy for organic degradation efficiently,which has a promising prospect for wastewater treatment.Construction the semiconductor photocatalyst with excellent activity plays the key role in photocatalysis.Among these semiconductors,Bi₂O₃ is widely used in photocatalytic degradation of organic pollutants under visible light irradiation.However,rapid recombination of photogenerated electron-hole pairs leads to low quantum efficiency,which seriously restricts the further development of Bi₂O₃ based photocatalytic technology.In addition,the heterogeneous photo-Fenton technology is also widespread applied for degradation of organic pollutants,which can continually and efficiently release·OH.However,the Fenton regents run off easily during valence state changes,meanwhile,low efficiency of electron separation and migration restrict its further practical application.In this study,In view of the above problems,the photocatalytic process of Bi₂O₃ and modified carbon nitrite（C₃N₄por）with ability of H₂O₂ generation is constructed for a self-driven photo-Fenton system,where much more attention are put into the required addition of H₂O₂ during heterogeneous photo-Fenton process.In order to improve the photocatalytic activity of the whole system,interfacial charge transfer has been employed.The specific research contents were as follows:（1）Using Bi（NO₃）₃?5H₂O as raw material,the Bi₂O₃ microspheres with a particle size of about 2μm are synthesized by hydrothermal.The influence of porphyrin content in C₃N₄por for H₂O₂ generation is investigated.It is revealed from experimental results that 0.1 wt%content of porphyrin in C₃N₄por has the best H₂O₂ generation capacity.Therefore,Bi₂O₃/C₃N₄por0.1 shows the highest photocatalytic activity,and the removal rate of methyl orange reaches 87.6%under visible light irradiation for 60 min.To confirm the successful construction the self-driven photo-Fenton system,the amount of·OH in different as-prepared samples are characterized by ESR.（2）Fe（Ⅲ）clusters are grafted onto the surface of Bi₂O₃ through a simple method to trigger interfacial charge transfer（IFCT）,which can shrink the bandgap and strengthen absorption ability of Bi₂O₃.The experimental results show that the grafted Fe（Ⅲ）clusters could not only trigger the IFCT,but also accelerate photogenerated electrons transfer,which could form a Fenton-like process with H₂O₂ from C₃N₄por.Moreover,the grafted Fe（Ⅲ）clusters could reduce the recombination of photogenerated electron-holes and improve the quantum efficiency of the whole system.Therefore,Bi₂O₃/Fe/C₃N₄por exhibits excellent photocatalytic activity.The amount of holes in the different samples are detected by ESR analysis,which confirms that the IFCT is successfully induced by grafting Fe（Ⅲ）clusters and promotes the efficiency of the self-driven photo-Fenton system.