High temperature potentiometric carbon dioxide sensor with minimal interference to humidity

Abstract We report on the development of a potentiometric sensor with Li 3 PO 4 electrolyte and BaCO 3 -coated Li 2 CO 3 sensing electrode for measuring CO 2 over a wide range of concentrations (500 ppm to 20%) at 500 °C with minimal interference to humidity. The active element in the sensing electrode for CO 2 detection is Li 2 CO 3 . However, sensors with just Li 2 CO 3 electrodes showed interference from humidity, which was eliminated by use of the BaCO 3 layer. Infrared spectroscopy as well as electrode preparations involving heating above the eutectic temperature of BaCO 3 –Li 2 CO 3 suggests that the BaCO 3 layer wets the Li 2 CO 3 electrode surface, making it more hydrophobic and thereby reducing the interference from humidity.

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