Construction and mechanism of a highly efficient and stable Z-scheme Ag3PO4/reduced graphene oxide/Bi2MoO6 visible-light photocatalyst

Abstract

A novel Ag₃PO₄/reduced graphene oxide/Bi₂MoO₆ (Ag₃PO₄/RGO/Bi₂MoO₆) Z-scheme photocatalyst has been successfully prepared by a precipitation-solvothermal method. The composition, morphology, structure and optical properties of the ternary composite were thoroughly investigated. The obtained Ag₃PO₄/RGO/Bi₂MoO₆ composite displayed significantly enhanced photocatalytic activity for the degradation of methylene blue (MB) under visible light irradiation, and its degradation rate (0.14575 min⁻¹) was approximately 2.34, 2.63 and 4.97 times faster than that of the Ag₃PO₄/Bi₂MoO₆ composite, pure Ag₃PO₄ and Bi₂MoO₆, respectively. Meanwhile, the Ag₃PO₄/RGO/Bi₂MoO₆ composite exhibited better stability compared with pure Ag₃PO₄ after four consecutive reuses. In addition, it shows good photodegradation efficiency for five other dyes under visible light irradiation. The improved photocatalytic performance and stability could be ascribed to the larger surface area, extended visible-light absorption capability and high-efficiency separation of electron–hole pairs of the Ag₃PO₄/RGO/Bi₂MoO₆ composite. Furthermore, RGO could act as a charge transmission bridge to accelerate the electron transfer from Ag₃PO₄ to Bi₂MoO₆ (Ag₃PO₄ → RGO → Bi₂MoO₆) in this Z-scheme system; thus the photocorrosion of Ag₃PO₄ and the recombination of charge carriers were effectively suppressed. The energy band structure and free radical capturing experiments proved that the electrons in the conduction band (CB) of Bi₂MoO₆ had stronger reducibility and the holes in the valence band (VB) of Ag₃PO₄ had higher oxidizability. Simultaneously, combined with the results of PL spectroscopy and photoelectrochemical measurements, the mechanism of Z-scheme charge transfer in the Ag₃PO₄/RGO/Bi₂MoO₆ composite was further confirmed. This study provides an idea for improving the anti-photocorrosion and photocatalytic performance of photosensitive semiconductors.