Study on the mechanism of photocatalytic activity enhancement of Ag/Ag3PO4/PDI-2 supramolecular Z-scheme heterojunction photocatalyst

In this paper, a new supramolecular Z-scheme heterojunction photocatalyst, designated as Ag/Ag₃PO₄/Perylene diimide organic molecules after secondary acid-base self-assembly (PDI-2), was synthesized through precipitation and photoreduction techniques. Ag/Ag₃PO₄/60 %PDI-2 (APP-6) exhibited the best photocatalytic activity due to the synergistic effect of Z-scheme heterojunction and surface plasmon resonance (SPR) effect of Ag nanoparticles (Ag NPs). Under visible light (λ > 420 nm), the degradation efficiency of APP-6 for Rhodamine B (RhB) and Bisphenol A (BPA) was 99.7 % and 90.7 %, respectively. Additionally, PDI-2 was transformed into smaller nanoclusters, which increased the specific surface area of the photocatalyst, and reduced the charge transport distance. Moreover, APP-6 exhibited the smallest electrochemical impedance, the largest photocurrent, the smallest fluorescence lifetime. Free radical trapping experiments showed that •O₂⁻ was the main reactive group and a possible photocatalytic mechanism was proposed by combining the Ultraviolet–visible diffuse reflectance spectrophotometer (UV–vis DRS) and the Mott-Schottky plots.