Photocatalytic degradation of tetracycline by <scp> WO ₃ </scp> / <scp> Bi ₃ NbO ₇ </scp> S‐scheme heterojunction photocatalyst

Abstract The construction of a heterojunction is an effective method to improve the separation of photo‐excited electrons and holes and in turn to enhance the photocatalytic activity of a single component photocatalyst. In this work, a heterojunction WO 3 /Bi 3 NbO 7 was prepared by impregnation of WO 3 nanoparticles into Bi 3 NbO 7 precursor followed by calcination. The prepared samples were characterized by techniques like x‐ray diffraction (XRD), Brunauer‐Emmett‐Teller (BET) specific surface area analysis, scanning electron microscope (SEM), transmission electron microscope (TEM), x‐ray photoelectron spectroscopy (XPS), UV‐vis diffuse reflectance spetrum (UV‐vis DRS), total organic carbon (TOC) analysis and electrochemical test. The photocatalytic performance was evaluated by investigation of tetracycline (TC) degradation under stimulated sunlight. The results showed that the heterojunction greatly improved the photocatalytic activity of Bi 3 NbO 7 under stimulated sunlight irradiation, beneficial to the effective separation of photo‐generated electrons and holes. The suitable Bi/W molar ratio is necessary to construct an effective heterojunction WO 3 /Bi 3 NbO 7 . The TC degradation efficiency of 85% was obtained on sample with Bi/W molar ratio of 2. The WO 3 /Bi 3 NbO 7 exhibited good reusability that TC degradation efficiency declined from 85% to 76% after five cycles of use. An S‐scheme mechanism was proposed for degradation of TC on WO 3 /Bi 3 NbO 7 heterojunction. This work provided a method for improving the photocatalytic activity of Bi 3 NbO 7 photocatalyst and may be applied to the wastewater treatment processes after further investigations in feasibility to industrial application.