Enhanced photocatalytic activity of a visible-light-driven ternary WO3/Ag/Ag3PO4 heterojunction: a discussion on electron transfer mechanisms

WO3/Ag3PO4 with different weight ratios were prepared by ultrasonic assisted two-step deposition method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectroscopy (PL) and transmission electron microscopy (TEM). The photocatalytic activities of all samples were evaluated by the degradation of rhodamine B (RhB) under visible light irradiation. WA-60 shows the highest photocatalytic activity in the WA-x series composite, while the photocatalytic activity of WAA-60 is the best among all samples. The free radical trapping experiments show that photogenerated holes (h+) are the main active species. The Ag nanoparticles produced by the decomposition of Ag3PO4 are located at the interface of Ag3PO4/WO3, which promotes the separation efficiency of photogenerated electrons and holes. To further explain the photocatalytic mechanism, electrochemical and physical tests are introduced to explore the flow of electrons inside the catalyst.