High-Temperature Formaldehyde-Sensing of WO3 Nanostructure Prepared by the SILAR Method: DFT Investigation of Gas Adsorption Properties

Tungsten oxide (WO3) was deposited through the successive ionic layer adsorption reaction (SILAR) method at low temperature. The polycrystalline monoclinic structure of deposited WO3 is confirmed by its x-ray diffraction (XRD) pattern. Sensing studies revealed that the nanostructured WO3 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 WO3 were analyzed using the density of states (DOS) and Mulliken population analysis for adsorption of oxygen and HCHO on the WO3 surface. A significant change in the Fermi energy was observed during oxygen and HCHO adsorption on the surface of WO3. 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.