Role of reactive oxygen species in the photocatalytic degradation of methyl orange and tetracycline by Ag3PO4 polyhedron modified with g-C3N4

Abstract

A rational hydrothermal method was used to prepare Ag3PO4 polyhedron modified with g-C3N4. The as-obtained samples were characterized by XRD, FESEM, FT-IR, XPS and UV–vis DRS. SEM images showed that as-synthesized Ag3PO4 sample consisted of polyhedron-shaped particles, and the sheet-like g-C3N4 was deposited on the surface of Ag3PO4 polyhedron to construct a compound structure. The role of photo-induced reactive oxygen species in both Ag3PO4 and g-C3N4/Ag3PO4 suspension for methyl orange and tetracycline degradation was investigated. As-obtained g-C3N4/Ag3PO4-1 composite exhibited a higher catalytic activity toward methyl orange degradation than that of pristine Ag3PO4 polyhedron mainly because of the enhanced O2− generation ability of g-C3N4/Ag3PO4-1 under visible light illumination; however, when tetracycline was used as the target pollutant, the photocatalytic activity of Ag3PO4 polyhedron was almost equal to that of g-C3N4/Ag3PO4-1 because more H2O2 was generated in Ag3PO4 suspension. According to the results of free radical trapping experiment and photoelectrochemical test, the visible light-driven photocatalytic mechanism of g-C3N4/Ag3PO4 hybrid for the removal of methyl orange and tetracycline was put forward. This work may provide a new insight into the catalytic activity evaluation of Ag3PO4-based composite photocatalysts.