Construction of hierarchically structured Bi2MoO6/g-C3N4/kaolinite S-scheme heterojunction photocatalyst for the efficient removal of formaldehyde and tetracycline under visible light

A novel hierarchically structured Bi₂MoO₆/g-C₃N₄/kaolinite ternary S-scheme heterojunction photocatalyst was synthesized by a simple calcination crystallization and solvothermal method, with exfoliated kaolinite as the carrier. Detailed analysis of the structure and morphology of the composite was conducted through a series of characterization techniques. The results indicate that the incorporation of kaolinite notably enhanced the photocatalytic performance of the composite. Kaolinite not only acts as a carrier, providing a high specific surface area and abundant adsorption sites, but also facilitates the migration and separation of photogenerated carriers through its unique layered structure and surface chemical properties. Consequently, this ternary composite exhibits excellent degradation performance towards tetracycline and formaldehyde under visible light irradiation, with reaction rate constants that are 15.5 times and 8.05 times higher than that of pure g-C₃N₄, respectively. Radical scavenger experiments reveal that hydroxyl radical (•OH) is the primary active specie. Finally, we discuss the synergistic mechanism of kaolinite in the composite, including its enhancement of light capture ability, improvement of charge separation efficiency, and promotion of active species generation. Overall, this study provides new insights for developing highly efficient and stable kaolinite-based visible-light-driven materials for environmental remediation.