HIGH-PERFORMANCE SOLID-ELECTROLYTE CARBON-DIOXIDE SENSOR WITH A BINARY CARBONATE ELECTRODE

A compact solid-state CO2 sensor based upon an Na+-conducting solid electrolyte (NASICON) can be improved drastically in response time and water vapour resistance by the use of a binary carbonate electrode of BaCO3 - Na2CO3. For a wide range of CO2 concentration from 4 to 400 000 ppm, the electromotive force (e.m.f.) examined at 550-degrees-C follows a Nernst equation correspondence to a two-electron reaction of CO2, with a 90% response time as short as 8 s or less. Water vapour hardly affects the sensor characteristics, in contrast to the case of a pure Na2CO3 electrode. The structure and CO2-sensing mechanism of the binary carbonate electrode are also discussed.