A Stable Solid-Reference Electrode of BiCuVOx/Perovskite-Oxide for Potentiometric Solid Electrolyte CO2 Sensor

A laminated solid-reference electrode of BiCuVOx (Bi2Cu0.1V0.9O5.35)/perovskite-oxide (La0.6Sr0.4Co0.78Ni0.02Fe0.2O3) was developed for a NASICON (Na3Zr2Si2PO12; Na+ conductor)-based potentiometric CO2 sensor. The fabricated electrochemical cell expressed as, CO2, O2/Au (sensing electrode)/Li2CO3-BaCO3 (auxiliary phase)/NASICON/BiCuVOx/BiCuVOx-perovskite-oxide (reference electrode)/O2, responded well to changes in CO2 concentration (100-400 ppm) at 450°C under high humid conditions (88%RH). The potential of the developed reference electrode was stable and exhibited little interference by water vapor. Furthermore, the reference electrode potential did not response to CO2 even after the BiCuVOx layer was contaminated with carbonate, indicating a good stability of BiCuVOx against CO2. The sensor device attached with the laminated solid-reference electrode showed a good warming-up characteristic, i.e., the electromotive force (EMF) of the device reached a steady and constant value when the sensor operation is re-started even after the sensor was exposed to humid air containing CO2 at room temperature.