Miniaturized Amperometric Solid Electrolyte Carbon Dioxide Sensors

A miniaturized electrochemical carbon dioxide (CO2) sensor using Na3Zr2Si2PO12 (NASICON) as a solid electrolyte has been fabricated and demonstrated. Microfabrication techniques were used for sensor fabrication to yield a sensing area around 1.0 mm x 1.1 mm. The NASICON solid electrolyte and the Na2CO3/BaCO3 (1:1.7 molar ratio) auxiliary electrolyte were deposited by sputtering in between and on top of the interdigitated finger- shaped platinum electrodes. This structure maximizes the length of the three-contact boundary (electrode, solid electrolyte, and auxiliary electrolyte), which is critical for gas sensing. The robust CO2 sensor operated up to 600ºC in an amperometric mode and attempts were made to optimize sensor operating parameters. Concentrations of CO2 between 0.02% and 4% were detected and the overall sensor performance was evaluated. Linear response of sensor current output to ln[CO2 concentration] ranging from 0.02% to 1% was achieved.