Abstract: In this study, a Fe₂O₃/g-C₃N₄ heterojunction photocatalyst was synthesized via a straightforward thermal polymerization approach. The material's structural features were thoroughly characterized using techniques such as XRD, XPS, and TEM. Furthermore, photoelectrochemical measurements were employed to systematically investigate the separation and migration behavior of photogenerated charge carriers. Tetracycline, a representative antibiotic contaminant, was selected as the target pollutant to evaluate the catalytic degradation efficiency and elucidate the underlying mechanism. Experimental results demonstrated that the as-prepared heterojunction catalyst achieved a tetracycline degradation efficiency of 99.5% within 90 minutes, with a reaction rate constant 30.3 times higher than that of pristine g-C₃N₄. After loading g-C₃N₄ on Fe₂O₃, the band gap width is effectively reduced, extending the light response range to the visible light region. The formed type-II heterojunction significantly promotes the separation and transfer efficiency of photogenerated carriers. Mechanistic analysis revealed that under PMS activation, the Fe₂O₃/g-C₃N₄ system generates various reactive species,including h⁺, .O^2-, ¹O₂， and .OH,that collectively contribute to pollutant decomposition. Additionally, the efficient Fe²⁺/Fe³⁺ redox cycle ensures excellent recyclability, maintaining high activity over five consecutive cycles.

Key words: heterojunction, g-C₃N₄, photo-Fenton oxidation reaction, tetracycline, persulfate