Interfacial carbon-regulated charge transfer and ROS evolution in Ag₃PO₄ for enhanced photo-persulfate activation

Conventional Ag₃PO₄ photocatalysts suffer from severe photocorrosion and inefficient reactive oxygen species (ROS) evolution. Herein, we constructed a biochar-supported Ag₃PO₄ (BC/Ag₃PO₄) composite to significantly reconfigure interfacial charge transfer in a coupled photo-peroxydisulfate (photo-PS) system for tetracycline (TC) degradation. The system exhibits remarkable synergistic enhancement, achieving a rate constant of 0.1512 min^-1 (6.61- and 12.92-fold increases over individual photocatalysis and PS systems). Mechanistic investigations reveal that BC acts as an interfacial electron mediator and adsorption regulator, facilitating interfacial electron redistribution and promoting preferential PS activation. This interfacial modulation induces a hybrid ROS microenvironment characterized by a radical-dominated oxidation framework (OH^• and SO₄^•-), synergistically coupled with interfacially regulated O₂^•- and ¹O₂ pathways. Notably, the introduction of BC induces a non-additive redistribution of ROS contributions through interfacial regulation, rather than a simple enhancement of radical generation, thereby simultaneously improving degradation efficiency, suppressing Ag₃PO₄ photocorrosion, and maintaining over 92.66% catalytic activity after five cycles. The BC/Ag₃PO₄+ photo-PS system accelerates TC degradation and redirects it to less toxic pathways, coupling efficiency with detoxification. This work presents an interface-driven strategy to regulate charge transfer and ROS evolution in photo-PS systems, providing mechanistic guidance for designing carbon-based semiconductor composites for environmental remediation.