Enhanced visible light photocatalytic activity of the needle-like SrMoO₄ decorated g-C₃N₄ heterostructure for degradation of tetracycline

Needle-like SrMoO₄ was prepared by precipitation and calcination, and SrMoO₄/g-C₃N₄ binary composites were successfully prepared by wet impregnation. Their phase structure, chemical composition, morphology and light absorption properties were analyzed by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence (PL) and examination of the photocurrent responses. The effects of different loading ratios, the initial concentration of pollutants and the initial pH on the photocatalytic properties of the composites were investigated. The results showed that the SrMoO₄/g-C₃N₄ composite with a SrMoO₄ loading ratio of 20% exhibited the best visible light catalytic activity for the degradation of tetracycline (TC) at pH = 9, and the degradation rate of TC (10 mg L⁻¹) could reach 80% after 14 min of visible light irradiation. Active species trapping experiments revealed that ˙O₂⁻ and h⁺ were the active species in the reaction process. The efficient catalysis benefited from the construction of a type II heterojunction interface between SrMoO₄ and g-C₃N₄, which could broaden the absorption range of visible light and improve the separation efficiency of photogenerated electrons and holes.