High-Temperature Formaldehyde-Sensing of WO 3 Nanostructure Prepared by the SILAR Method: DFT Investigation of Gas Adsorption Properties

Tungsten oxide (WO 3 ) was deposited through the successive ionic layer adsorption reaction (SILAR) method at low temperature. The polycrystalline monoclinic structure of deposited WO 3 is confirmed by its x-ray diffraction (XRD) pattern. Sensing studies revealed that the nanostructured WO 3 has a good response towards formaldehyde (HCHO) at 350°C. A response time of 28 s was observed for 5 ppm HCHO. Density functional theory (DFT) studies were performed to understand the detection mechanism based on the lattice plane growth orientation. The electronic properties of the WO 3 were analyzed using the density of states (DOS) and Mulliken population analysis for adsorption of oxygen and HCHO on the WO 3 surface. A significant change in the Fermi energy was observed during oxygen and HCHO adsorption on the surface of WO 3 . The computational results were compared with the proposed HCHO detection mechanism. The results obtained through the present work highlight the possibilities of developing a sensor to detect HCHO concentrations at the ppm level.