Sensing properties and mechanism of a planar carbon dioxide sensor using magnesia-stabilized zirconia and lithium carbonate auxiliary phase

Abstract

A planar electrochemical device using MgO-stabilized zirconia (MSZ) and Li₂CO₃ has been fabricated for potentiometric sensing of CO₂. The emf response of the device to CO₂ followed the Nernst equation well in the concentration range 100–2000 µl l^–1 at 500–650 °C, and was kept unchanged with a variation in the concentration of coexistent O₂, NO, NO₂, H₂ or H₂O. The rates of response and recovery were fairly rapid, attaining 90% of the changes in 10 s and 2 min, respectively, for 100–1000 µl l^–1 CO₂ at 550–600 °C. The electrochemical chain as well as the emf response to CO₂ of the novel device can be explained by considering the formation of Li₂ZrO₃ between MSZ (O^2– conductor) and Li₂CO₃(Li⁺ conductor) as an ‘ionic bridge’.