Preparation of network-like ZnO–FeWO4 mesoporous heterojunctions with tunable band gaps and their enhanced visible light photocatalytic performance

Abstract

Novel mesoporous ZnO–FeWO₄ (Zn–FeWO₄) heterojunctions with network-like structure were synthesized with a combination of thermal decomposition and hydrothermal methods. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N₂ sorption and Brunauer–Emmett–Teller (BET) surface area analysis, diffuse reflection spectroscopy (DRS) and photoluminescence spectroscopy (PL). The results showed that the size of FeWO₄ was reduced by the modification of ZnO. With the increasing molar ratio of ZnO to FeWO₄, the quantum size of FeWO₄ decreased from 11 nm to 4 nm, as is followed by a surprisingly band gap broadening. Photocatalytic activity toward the degradation of RhB under visible light irradiation was investigated. The optimum decomposition rate of RhB using the prepared 1.5Zn–FeWO₄ heterojunction was almost 39 and 9.7 times that of pristine ZnO and FeWO₄, respectively. The active species trapping experiments showed that the holes exhibited an obvious influence on the photocatalytic degradation process. The study on the mechanism showed that the enhanced photocatalytic activity was mainly ascribed to heterojunction construction and band gap broadening, which enhance the efficient transfer and the oxidation potential of holes. This heterojunction shows a potential industrial application to remove undesirable organics from the environment.