Infrared emission spectroscopic study of the adsorption of oxygen on gas sensors based on polycrystalline metal oxide films

Infrared emission spectroscopy (IRES) was used for studying in situ gas-surface interactions and adsorbed species on semiconducting metal oxides based gas sensors under working conditions. Regarding the key position of oxygen for the surface chemistry of oxides, the adsorption and reaction of oxygen was studied on screen printed films of polycrystalline WO3, AlVO4 and Co3O4 in the temperature range between 300 and 600°C. The role of the ionization of oxygen vacancies on the conductivity mechanisms and on the reaction to hydrocarbons will be discussed correlating the results of IRES and conductivity measurements. This work shows that IRES offers a direct access to the generation of free charge carriers due to changes in oxygen partial pressure and reactions with reducing gases.