Enhanced photoluminescence and photocatalytic performance of a TiO2–ZnWO4 nanocomposite induced by oxygen vacancies

Abstract

Titanium dioxide (TiO₂)–zinc tungstate (ZnWO₄) nanocomposite powder was prepared by a sol–gel procedure. The X-ray diffraction pattern (XRD) of the nanocomposite indicates that the crystallinity of TiO₂ is reduced by coupling with ZnWO₄. High resolution microscopic observation of the nanocomposite reveals the intimate contacts formed between the TiO₂–ZnWO₄ interfaces. The composite’s structure slightly reduces the aggregation of the unmixed TiO₂ and ZnWO₄, leading to a larger surface area. The photoluminescence (PL) spectrum of the nanocomposite exhibits a prominent broad emission band centered at about 470 nm, compared with that of the pure ZnWO₄. Gaussian fitting of the PL peak of the nanocomposite suggests a reduced number of oxygen defects on the ZnWO₄ surface. This is further confirmed by X-ray photoelectron spectroscopy (XPS) analysis of the nanocomposite, and the number of oxygen defects on the surface of TiO₂ is demonstrated to be increased by coupling with ZnWO₄. The photocatalytic activity of the nanocomposite was evaluated by degrading methyl orange under UV light irradiation. The results showed that the photocatalytic performance of TiO₂ is much improved through coupling with ZnWO₄.