Redox-mediating centers overcome activity-stability trade-off in photocatalysis: Singlet oxygen generation via dual pathways on Ce-doped Ag3PO4

Ag 3 PO 4 exemplifies the persistent activity-stability trade-off in photocatalysis, where its high photo-oxidation capability is inevitably undermined by severe photocorrosion. This work breaks this coupling by constructing Ce 3 + /Ce 4+ redox-mediating centers within Ag 3 PO 4 . The optimal catalyst achieves near-complete degradation of tetracycline antibiotics within 30 min, with a rate constant increased by approximately 3.2 times, and maintains over 85% of its initial activity after five cycles, whereas pristine Ag 3 PO 4 undergoes complete deactivation. Singlet oxygen ( 1 O 2 ) is identified as the dominant species, and a dual-pathway generation mechanism that bypasses the material's inherent constraints is unveiled: alongside the • OOH‑mediated hole oxidation pathway, the Ce 3+ /Ce 4+ couple catalyzes a sequential two‑electron O 2 reduction to H 2 O 2 and its subsequent Fenton‑like conversion to 1 O 2 . Combined spectroscopic and theoretical analyses confirm that these centers act as exclusive electron traps, diverting photoexcited electrons away from Ag + sites—thus inhibiting Ag + → Ag 0 corrosion—and directing both electron and hole densities toward themselves in the excited state. This work demonstrates that engineering atomically dispersed redox mediators can decouple charge separation from detrimental surface reactions, providing a general strategy to simultaneously confer high activity and robust stability upon otherwise fragile photocatalysts.