Construction of an S-scheme g-C₃N₄/MIL-125(Ti) Heterojunction for Highly Efficient Photocatalytic Degradation of Tetracycline

Abstract

This study investigates the degradation efficiency of a hydrothermally synthesized g-C₃N₄/MIL-125(Ti) heterojunction photocatalyst towards tetracycline. Its performance was compared with those of pure g-C₃N₄ and MIL-125(Ti). The composition, structure, and morphology of the synthesized composite catalysts were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (SEM), diffuse reflectance UV-visible spectroscopy (DRS), and Brunauer-Emmett-Teller (BET) analysis of specific surface area and pore size distribution. Spectrophotometric measurements of tetracycline concentration and radical-quenching experiments revealed that the g-C₃N₄/MIL-125(Ti) heterojunction photocatalyst achieved a 96.8% degradation rate for a 50 mg/L tetracycline solution within 120 minutes, significantly surpassing the individual components. Quenching tests identified the superoxide radical (·O₂⁻) as the primary active species. Computational results indicate that the trapezoidal heterojunction photocatalyst, g-C₃N₄/MIL-125(Ti), effectively promotes photoinduced charge separation while retaining strong redox capability, which likely accounts for its high catalytic activity in the efficient degradation of tetracycline.

Keywords

g-C₃N₄/MIL-125(Ti) / S-scheme heterojunction / tetracycline / photocatalytic degradation / photocatalytic materials / charge separation

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