Stabilizing surface oxygen vacancies with Ag nanoparticles on Bi4Ti3O12 for durable photocatalytic removal of urban pollutants.

Abstract

Surface oxygen vacancies (VOs) in bismuth-based layered photocatalysts are highly active yet prone to deactivation via refilling by ambient oxidants, posing a major stability challenge for their practical application in urban environmental remediation. To address this, Ag nanoparticles were in-situ photodeposited onto VO-rich Bi4Ti3O12 (BTO-VO) to construct Ag@BTO-VO-n composites with varied Ag loadings. The optimal catalyst Ag@BTO-VO-20 displays exceptionally enhanced photocatalytic activity, with both its degradation kinetics and turnover frequency (TOF) reaching levels over 28.5 and 22.7 times higher than those of pristine BTO and BTO-VO, respectively. This performance improvement originated from optimized charge carrier dynamics, where the synergistic effect of VOs and Ag/BTO-VO Schottky junction prolonged carrier lifetime by 2.1 times, enhanced photocurrents by 2.7-fold, and reduced interfacial charge-transfer resistance, leading to efficient charge separation. Mechanistic investigations identified superoxide radicals and holes as the primary active species. Crucially, Ag nanoparticles provide effective protection for the surface Vos through interfacial electron modulation and competitive O2 adsorption, thereby inhibiting their deactivation and ensuring catalyst stability. This was further validated by comparative EPR analysis of H2O2-filling experiment. This work elucidates a dual stabilization mechanism where Ag crucially prevents the healing of surface Vos, offering a strategic pathway to design durable and highly active layered photocatalysts for efficient purification of urban environmental pollutants.

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