High-Efficiency Visible-Light-Driven Ag₃PO₄/AgI Photocatalysts: Z-Scheme Photocatalytic Mechanism for Their Enhanced Photocatalytic Activity

Abstract

High-efficiency visible-light-driven Ag3PO4/AgI photocatalysts with different mole fractions of AgI have been synthesized via an in-situ anion-exchange method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and UV–vis diffuse reflectance spectroscopy (DRS). Under visible light (>420 nm), the Ag3PO4/AgI photocatalysts exhibit enhanced photocatalytic activity compared to pure Ag3PO4 or AgI for the degradation of methyl orange and phenol, and the highest activity is reached by the Ag3PO4/AgI hybrid photocatalyst with 20% of AgI. The quenching effects of different scavengers suggest that the reactive h+ and O2•– play the major role in the MO degradation. Detailed X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis reveals that Ag nanoparticles (NPs) form on the surface of Ag3PO4/AgI in the early stage of the photocatalytic oxidation process, thus leading to the transformation from Ag3PO4/AgI to Ag3PO4/AgI@Ag. The excellent photocatalytic activity of the Ag3PO4/AgI photocatalysts can be ascribed to the efficient separation of photogenerated electron–hole pairs through a Z-scheme system composed of Ag3PO4, Ag, and AgI, in which the Ag nanoparticles acted as the charge transmission bridge. The Ag3PO4/AgI hybrid remains good photocatalytic activity after five cycling runs.