TiO2(B) nanoparticle-functionalized WO3 nanorods with enhanced gas sensing properties

Abstract

In this work, TiO₂(B) nanoparticle (NP)-functionalized WO₃ nanorods (NRs) were synthesized by a two-step solution strategy, with a hydrothermal process for WO₃ NRs and hydrolyzation of Ti(OBu)₄ for the functionalization of TiO₂(B) NPs. Various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), were employed to investigate the morphology, microstructure, crystalline nature and chemical composition of the prepared TiO₂(B) NP-functionalized WO₃ NRs. SEM and TEM results revealed that the TiO₂(B)–WO₃ composite showed a rod-like nanostructure with a diameter in the range from 93 to 154 nm and a rough surface, which could increase the accessible surface area and the amount of surface active sites, thus improving the properties or performance of the as-prepared composite NRs. XRD and XPS analysis clearly verified that monoclinic TiO₂(B) NPs, a metastable polymorph of TiO₂, were successfully supported on the WO₃ NRs. Gas sensing measurement results for several common reductive organic gases such as acetone, ethanol, ether, methanol and formaldehyde demonstrated that the sensor based on the as-obtained TiO₂(B) NP-functionalized WO₃ NRs exhibited obviously enhanced responses compared with a pure WO₃ NR based sensor, as well as fast response–recovery speeds, good reproducibility and good stability, indicating their promising application in gas sensors. The excellent gas sensing performance could be attributed to the unique 1D rod-like nanostructure with a rough surface, the existence of TiO₂–WO₃ heterojunctions and the catalytic effect of the TiO₂(B) NPs. The as-prepared TiO₂(B) NP-functionalized WO₃ NRs will also have very good prospects in electrochromic devices and catalysis applications.