NO2 sensing properties of WO3 porous films with honeycomb structure.

WO 3 porous films (WPFs) were synthesized by a non-hydrolytic sol-gel (NHSG) method using WCl 6 , C 2 H 5 OH, and C 3 H 7 NO as the precursors. The polyethylene glycol (PEG) was employed as a porogen to prepare the porous structure. The microstructures of WPFs were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Nitrogen adsorption-desorption isotherms were used to characterize the specific surface areas of the samples. The results indicated that the honeycomb-like WPFs were assembled by numerous WO 3 nanoparticles with the diameter of 20–60 nm. Gas sensing measurements showed that the peak sensor response to NO 2 was obtained at the operating temperature of 100 °C. The sensor based on WPFs showed excellent reversibility and fast response to NO 2 at various operating temperatures and NO 2 concentrations. The sensor also exhibited a significant NO 2 selectivity compared with NH 3 , SO 2 , CH 3 OH, and C 2 H 5 OH, demonstrating a promising application in detecting NO 2. The porous structure formation process of the WPFs was analyzed and gas sensing mechanism based on electron depletion theory as well as first principle calculations were discussed. Image 1 • WO 3 porous films with honeycomb-like nanostructure were synthesized by a non-hydrolytic sol-gel technique. • WO 3 porous films were assembled by numerous crystalline nanoparticles with the diameters of 20–60 nm. • Gas sensor based on WO 3 porous films showed high response and excellent reproducibility to NO 2. • The porous structure formation and sensing mechanism of WO 3 porous films were discussed. [ABSTRACT FROM AUTHOR]