WO₃ Nanoparticles on Nanosheets of Phosphorus-Doped g-C₃N₄ as S-Scheme Heterojunction Photocatalysts for the Degradation of Tetracycline

The S-scheme heterojunctions effectively boost the charge separation and strong redox capacities. Therefore, designing S-scheme heterojunction systems with improved photocatalytic properties is considered an efficient strategy for solving acute environmental problems. In this study, phosphorus (P) atoms were doped onto g-C3N4 nanosheets via vitamin B12 (VB12) sources and then decorated with WO3 nanoplates to form an S-scheme P-CN/WO3 heterojunction photocatalyst. The X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) findings revealed the successful decoration of WO3 nanoplates on P-CN nanoplates. Also, X-ray photoelectron spectroscopy (XPS) confirmed the doping of P atoms on the g-C3N4 nanosheets. The results from the electrochemical analysis, radical-related experiments, and work function (Φ) further showed the formation of S-scheme heterojunctions with effective interfacial charge transfer. Therefore, the S-scheme P-CN/WO3 heterojunction material revealed the highest reaction rate constant (0.0185 min–1) compared to pure P-CN (0.0061 min–1) and WO3 (0.0041 min–1) for degradation of tetracycline (TC) under 30 W light-emitting diode (LED) light irradiation. The response of P-CN and WO3 to visible light, the defects in the P-CN structure, the proper band gap, and the textural properties resistant against reactive oxygen species (ROS) led to the suitable performance of this photocatalytic system. The current study highlights the industrial manufacture of S-scheme heterojunction catalysts in removing pollutants from wastewater.