NO and NO2sensing properties of WO3and Co3O4based gas sensors

Abstract

Semiconductor-based gas sensors that use n-type WO3or p-type Co3O4powder were fabricated and their gas sensing properties toward NO2or NO (0.5-5 ppm in air) were investigated at 100 °C or 200 °C. The resistance of the WO3-based sensor increased on exposure to NO2and NO. On the other hand, the resistance of the Co3O4-based sensor varied depending on the operating temperature and the gas species. The chemical states of the surface of WO3or those of the Co3O4powder on exposure to 1 ppm NO2and NO were investigated by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. No clear differences between the chemical states of the metal oxide surface exposed to NO2or NO could be detected from the DRIFT spectra. © 2013 by the authors; licensee MDPI, Basel, Switzerland.