High temperature potentiometric carbon dioxide sensor with minimal interference to humidity

We report on the development of a potentiometric sensor with Li3PO4 electrolyte and BaCO3-coated Li2CO3 sensing electrode for measuring CO2 over a wide range of concentrations (500 ppm to 20%) at 500 degrees C with minimal interference to humidity. The active element in the sensing electrode for CO2 detection is Li2CO3. However, sensors with just Li2CO3 electrodes showed interference from humidity, which was eliminated by use of the BaCO3 layer. Infrared spectroscopy as well as electrode preparations involving heating above the eutectic temperature of BaCO3-Li2CO3 suggests that the BaCO3 layer wets the Li2CO3 electrode surface, making it more hydrophobic and thereby reducing the interference from humidity. (C) 2009 Elsevier B.V. All rights reserved.