WO3 nanocrystals decorated Ag3PO4 tetrapods as an efficient visible-light responsive Z-scheme photocatalyst for the enhanced degradation of tetracycline in aqueous medium

A series of WO3/Ag3PO4 composites with varying amounts of WO3 were successfully synthesized by a surfactant-free hydrothermal method and utilized for the photocatalytic degradation of tetracycline (TC) under visible-light irradiation. The formation of a composite structure with the decoration of WO3 nanocrystals on the surface of tetrapod-like Ag3PO4 was clearly seen in the materials characterization. The surface of Ag3PO4 tetrapods was found to be homogenously decorated with WO3 nanocrystals depending on their incremental amount, and an adjacent contact between the coupling materials was resulted that instigated the formation of heterointerfaces in the composites. The visible light absorption of WO3 was significantly improved by its coupling with Ag3PO4 tetrapods. The photoluminescence, electrochemical impedance and photocurrent density analyses indicated the increased life time of the charge carriers with reduced electron-hole pair recombination rate. The photocatalytic activity results had shown that within 24 min of visible light irradiation, the 50 % WO3/Ag3PO4 composite achieved 96 % TC degradation with a TC mineralization efficiency of 15.4 %. The enhanced photocatalytic activity of the composites could be attributed to the facile separation of the photoinduced charge carriers through a Z-scheme type charge transfer mechanism at the heterointerface. The scavenger studies specified the primary role of holes and hydroxyl radicals in the oxidative degradation of TC. Additionally, the 50 % WO3PO4 composite was effectively reused for four cycles of TC degradation with a gradual loss in its activity, whereas the Ag3PO4 tetrapods suffered a rapid photocorrosion. It validates the superior role of charge transfer process in the photocorrosion inhibition of Ag3PO4 tetrapods.