Hydrothermal synthesis and gas sensing properties of hexagonal and orthorhombic WO3 nanostructures

Hollow cauliflower-like hexagonal WO3 and cuboid-like orthorhombic WO3 nanostructures were successfully synthesized via a simple hydrothermal method with the assistance of different surfactants. The products were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The possible formation mechanisms of the different WO3 morphologies were proposed and the gas sensing properties were also investigated. Our research indicated that the different morphology and crystal phase were crucial for the dissimilarity of the gas sensing performance. The novel cauliflower-like WO3 sensor exhibited excellent CO sensing properties at 270 degrees C with higher and faster response, which may benefit from the hollow porous structure and the (001) reactive surfaces of the hexagonal phase. The sensing mechanism was discussed.