Two-stage hydrothermal process driven visible light sensitive photocatalytic m-ZnWO4/m-WO3 heterojunction composite materials

Abstract

The current study reports on the facile two-step hydrothermal synthesis of heterojunction m-ZnWO4/m-WO3 composite powders for visible light sensitive photocatalytic applications. The ZnWO4 particles start crystallizing on the surface of the WO3 powder in the second stage of the reaction in a basic medium. The phases of the composite powders were confirmed using x-ray diffraction analysis. The monoclinic cubic shaped WO3 and rod shaped ZnWO4 morphologies were disclosed from the field emission scanning electron microscope images. Strong interfacial adhesion between ZnWO4 and WO3 was unveiled from the high-resolution transmission electron microscopy study. The optimized composite 5ZW exhibits a calculated bandgap of 2.58 eV, positioning it within the visible light wavelength range (λ = 400–700 nm). Furthermore, there is a notable enhancement in the average lifetime of the electron–hole pair recombination rate, which is extended to 30.3 ns. The composite 5ZW demonstrated 96% methylene blue dye degradation efficiency within 420 min under visible light irradiation at pH 12. Due to the optimal phase fraction and strong interfacial adhesion between ZnWO4 and WO3, the heterojunction scheme seemed to be highly efficient in the 5ZW composite. Hence, it is believed that a two-step hydrothermal method can be a proficient route to prepare heterojunction composites m-ZnWO4/m-WO3 in alkali conditions with visible light active photodegradation efficiency.