Sensing functions to NO and O2 of Nb2O5- or Ta2O5-loaded TiO2 and ZnO

Variations in electro-conductivity with adsorption of NO and O2 were measured on metal oxide (Nb2O5, Ta2O5, WO3 and MoO3)-loaded TiO2 and ZnO. Each metal oxide enhanced the photo-sensitivity of the electro-conductivity of TiO2 and ZnO. Nb2O5/TiO2 was shown to be most sensitive to NO. The variations of IR spectra of Nb2O5/TiO2 with NO- and O2-adsorption were measured to discuss the active sites under photo-irradiation. Two types of adsorbed NO were estimated on Nb2O5/TiO2 by the IR spectroscopy. The sensing function was assumed to arise from the NO adsorbates which occupied O vacancies and diminished the electro-conductivity.