In situ synthesis of three-dimensional core–shell structure Bi2WO6/BiOCl and photocatalytic degradation of trinitrotoluene wastewater

Bi₂WO₆/BiOCl nanocomposites with three-dimensional core–shell structure were synthesized by a two-step hydrothermal method. The compounds were characterized by XRD, SEM, TEM, HR-TEM, EDX, SAED, XPS, PL, UV–Vis DRS, photoelectrochemical, and photodegradation experiments. The result showed that the catalytic activity of Bi₂WO₆/BiOCl nanocomposites was significantly better than that of Bi₂WO₆ and BiOCl. The effect of the amount of Bi₂WO₆ on the properties of the composite was studied. The result showed that the Bi₂WO₆/BiOCl with three-dimensional core–shell structure had the highest photocatalytic degradation efficiency for TNT, and the degradation rate reached 90% after 180 min of visible light irradiation. In the degradation process of TNT, the reaction rate of 4.5 Bi₂WO₆/BiOCl is the highest, which is 0.20057 min⁻¹. After 4 cycles, the degradation rate of TNT by 4.5 Bi₂WO₆/BiOCl remained at 80%. The free radical trapping experiments showed that the holes and superoxide anions played a major role in the photocatalytic degradation of TNT wastewater by 4.5 Bi₂WO₆/BiOCl. Based on the results of free radical trapping experiment, Mott-Schottky test, and ultraviolet–visible diffuse reflection spectroscopy, the reaction mechanism of enhancing photocatalytic activity was proposed.