Oxygen-induced spin-polarization in bulk g-C3N4 for piezo–photocatalytic degradation of antibiotics

The pervasive presence of antibiotics in natural water bodies has become a critical environmental and health concern. In this work, we have synthesized oxygen-doped graphitic carbon nitride (O-g-C 3 N 4 ) bulk via thermal condensation without any post processing, exhibiting a relatively high specific surface area of 42.053 m 2  g −1 and a reduced band gap to 2.56 eV. The O-g-C 3 N 4 bulk demonstrates the maximum piezo–photocatalytic degradation of ofloxacin (OFL) under blue-light LED irradiation, which perfectly matches with the maximum transmittance wavelength of water, minimizing light absorption loss during propagation in water. Taking advantages of oxygen-doping induced spin-polarization, the O-g-C 3 N 4 bulk achieves nearly complete (99.9 %) degradation of OFL within 12 min under blue-light LED illumination with 50 W power, and the complete degradation time further decreases to 6 min with the assistance of 80 W ultrasonication. The synergistic effect of combining photocatalysis with piezoelectricity is attributed that the ultrasound-induced piezoelectric field facilitates the generation of hydroxyl radicals and improves the separation of photogenerated electron–hole pairs. The findings contribute to sustainable solutions for antibiotic pollution challenges and advance the application of visible light piezo–photocatalysis.