Double-cell carbon dioxide sensor based on Li-K molten carbonate with electrochemically-supplied CO₂-O₂ reference

A carbon dioxide sensor using molten carbonate electrolyte with double-cell structure was examined; one cell was employed for electrochemical pumping of CO₂ and O₂ from ambient atmosphere and the other was used for sensing of the ambient CO₂ with the pumped CO₂-O₂ mixture as a reference gas. The sensor was operated at 600 °C for the sensing of CO₂-containing air. By sending appropriate current, the pumping cell could provide CO₂ and O₂ at 2/3 and 1/3 of the atmospheric pressure, respectively. The sensing cell showed EMF with respect to the CO₂ and O₂ partial pressures against the pumped CO₂-O₂ reference gas. The sensor could determine the partial pressure of CO₂ in the examined range of 26 to 1×10⁴ Pa (260-100,000 ppm).