Synergistic enhancement of charge separation and light absorption in a Z-scheme g-C3N4/Bi/BiPO4 photocatalyst for antibiotic degradation

Advancing novel photocatalytic systems for efficient antibiotic removal is a key strategy for sustainable water purification. However, it remains technically challenging to balance high charge separation efficiency with broad-spectrum light absorption. Herein, the g-C 3 N 4 /Bi/BiPO 4 composite photocatalyst featuring a Z -scheme heterojunction mediated by Bi nanoparticles was synthesized and systematically evaluated. This unique structure integrates surface plasmon resonance (SPR) to simultaneously enhance charge separation and visible light absorption, addressing limitations of traditional g-C 3 N 4 -based systems. Photoelectrochemical characterization confirmed its superior charge separation and rapid electron transfer. Energy band analyses via UV–Vis DRS, XPS valence, and Mott-Schottky tests revealed that the Z -Scheme heterojunction, formed through an internal electric field and mediated by Bi, effectively enhanced the processes of charge separation and light absorption synchronously. Under simulated solar light irradiation, the composite exhibited a 97.5 % tetracycline degradation rate within 90 min, with a reaction rate constant of 4.00 × 10 −2  min −1 , significantly outperforming individual g-C 3 N 4 and BiPO 4 catalysts. Reactive species trapping experiments identified ·OH, ·O 2 − , 1 O 2 and h + as the dominant reactive species in tetracycline degradation. Overall, this study provides a solid theoretical foundation and experimental support for the practical application of photocatalytic technology in wastewater treatment.