CARBON-MONOXIDE AND HYDROGEN DETECTION BY ANATASE MODIFICATION OF TITANIUM-DIOXIDE

From the viewpoint of industrial and automobile exhaust pollution control, a sensor capable of detecting and measuring the concentration of harmful gases such as carbon monoxide and hydrogen in the ambient is desired. This paper describes the development and use of a titania (TiO2)-based semiconducting oxide material as a reliable and rugged CO and H-2 gas sensor in the temperature range of 773 to 1073 K. Significant change in the sensing characteristic of the anatase modification of TiO2 was observed when admixed with an insulating second phase, such as alumina or yttria. In the case of TiO2-10 wt% Al2O3, the sensor response was found to be exclusively dependent on the hydrogen concentration alone; the presence of CO or CO2 did not affect the sensitivity. On the other hand, the sensor based on TiO2-10 Wt% Y2O3 showed increased sensitivity to CO and decreased sensitivity to H-2, compared to that of the undoped TiO2. Addition of elemental iron, in small concentration, to the two-phase mixture of titania and yttria seemed to further improve the sensitivity and selectivity of the latter to CO.