A review on WO3 based gas sensors: Morphology control and enhanced sensing properties

Tungsten oxide (WO3), a typical n-type gas-sensing material, has attracted considerable attention to detect various hazardous gases. Previous studies indicated that unique nanostructures are highly related to the sensing performances. So far, great advances have been achieved to design and fabricate diverse WO3 in different dimensional. However, it is still challenging to achieve high performances. To significantly enhance the gas-sensing properties, many strategies have been explored. In this review, the general approaches to tune the morphologies of WO3 are analyzed. Then, much more attention is particularly paid to improve the sensing-properties of WO3 based gas sensors. Firstly, the fundamental of WO3 based gas sensors is described. Secondly, various progresses to control the morphologies in 0-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) WO3 will be reviewed. Thirdly, the efficient strategies for the enhancement of gas-sensing properties based on WO3 will be discussed. Meanwhile, the enhancement mechanisms are taken into account as well. Finally, a perspective on the further development for WO3 synthesis and applications in gas sensors is proposed as well.