Construction of ultrathin C3N4/Bi4O5I2 layered nanojunctions via ionic liquid with enhanced photocatalytic performance and mechanism insight

• A ionic liquid induced strategy for the synthesis of ultrathin C3N4/Bi4O5I2 nanojunctions.
• The introduction of reactable ionic liquid was used for the formation of ultrasmall Bi4O5I2 nanosheets and the improvement of the dispersity of ultrathin C3N4, which contributed to the combination of ultrathin C3N4 and Bi4O5I2 together efficiently and further favor the construction of tight junction between the two.
• The 3 wt% C3N4/Bi4O5I2 nanojunctions exhibit the highest photocatalytic activity for removing the RhB and BPA in solution.
• The hole is the dominant species for the degradation of pollutants.

A novel visible-light-driven ultrathin C3N4/Bi4O5I2 layered nanojunctions photocatalyst was prepared via a facile solvothermal method in the presence of reactable ionic liquid 1-hexyl-3-methylimidazolium iodide ([Hmim]I). 1-hexyl-3-methylimidazolium iodide was served as I source, template and dispersing agent at the same time, which favored the formation of Bi4O5I2 ultrasmall nanostructure and good dispersivity among the ultrathin C3N4. A series of characterizations were employed to probe the structure, morphology, optical and electronic characteristics of the obtained ultrathin C3N4/Bi4O5I2 layered nanojunctions. Experiment results show that the ultrasmall Bi4O5I2 nanosheets were dispersed on the surface of ultrathin C3N4 uniformly and the compact heterostructures were constructed. The photocatalytic performance of the as-prepared samples was evaluated by the degradation of rhodamine B (RhB) and colorless endocrine disrupting chemical bisphenol A (BPA) under visible light irradiation. The ultrathin C3N4/Bi4O5I2 layered nanojunctions displayed much higher photocatalytic activity than the pure Bi4O5I2, in addition, 3 wt% ultrathin C3N4/Bi4O5I2 exhibited the highest activity. The enhancement of photocatalytic activity was ascribed to the well-distribution for ultrasmall Bi4O5I2 nanosheets on the ultrathin C3N4 surface and the formation of closely heterostructures that could favor the transfer and separation of photogenerated charge carriers. A possible photocatalytic mechanism based on the matched energy band structure and action mechanism of active species was proposed.

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