Synergistic photocatalytic degradation of tetracycline by Fe(II)/PMS and g-C3N5/BiVO4 S-scheme heterojunction: Mechanism and performance

Tetracycline (TC), a widely detected aquatic pollutant, poses significant ecological risks, necessitating the development of effective remediation strategies. Photocatalytic degradation, which converts TC into harmless CO 2 and H 2 O, offers a promising eco-friendly solution. This study successfully synthesized a novel 2D/3D g-C 3 N 5 /BiVO 4 (N-CN/BiVO 4 ) S-scheme heterojunction via a hydrothermal method. The optimized 5 % N-CN/BiVO 4 exhibited exceptional performance in activating the Fe 2+ /PMS system under visible light, achieving a 96.8 % TC removal efficiency with an apparent rate constant 4.4 times higher than that of BiVO 4 . Mechanistic studies, including ultraviolet photoelectron spectroscopy (UPS) and valence band X-ray photoelectron spectroscopy (VB-XPS), confirmed the S-scheme interfacial charge transfer pathway. Furthermore, radical quenching experiments revealed that the enhanced photocatalytic activity originated from the synergistic contribution of multiple reactive species ( OH, SO 4 − , O 2 − , h + , and 1 O 2 ), validating both the efficient activation of Fe 2+ /PMS and the proposed S-scheme charge transfer mechanism. This work presents an innovative approach for high-performance pollutant degradation by coupling an S-scheme heterojunction with the Fe 2+ /PMS activation system.