Titania-Based Miniature Potentiometric Carbon Monoxide Gas Sensors with High Sensitivity

Miniature, potentiometric, solid-state, carbon monoxide (CO) sensors with semiconducting oxide electrodes were investigated over the temperature range 500 degrees-700 degrees C. The effects of the electrochemical properties of the semiconducting oxides, after the addition of a catalyst and an alkaline metal oxide were evaluated in terms of the improvement in selectivity and response time. A sensor with high sensitivity and reversibility was obtained using a combination of an n- (titania) and p-type (composite titania with yttria and palladium) electrode to form a difference in the electrode equilibria. The device was able to measure a wide range of CO concentrations (10-16 000 ppm) with a high sensitivity to CO. A low-cost, rugged device could be fabricated because the sensing and reference electrodes were exposed to the same gaseous atmosphere. The results presented herein were attributed to the differential electrode equilibria mechanism, which comprises both semiconducting response and heterogeneous electrocatalysis contributions to the potentiometric sensor response.