Two kinds of materials, Bi2Cu0.1V0.9O 5.35 (BICUVOX) and NaCoO2, were investigated for their applicability as the counter electrode for a potentiometric CO2 sensor using NASICON (Na+ conductor, Na3Zr 2Si2PO12). The BICUVOX counter electrode was more stable than an Au counter electrode. Thermal cycling between the operating temperature (450°C) and room temperature under various conditions indicated the time needed for the BICUVOX electrode to reach the stationary potential after switching to the operating temperature was unacceptably long. NaCoO 2 was found unsuitable as a counter electrode material due to its reactivity with CO2. This reactivity was suppressed completely when NaCoO2 was coated with a layer of glass (SiO2: Na 2O: B2O3: Al2O3 = 44:20:31:5, in molar ratio). The glass-coated NaCoO2 electrode worked well as a counter electrode at 450°C. Thermal cycling indicated that the glass-coated NaCoO2 electrode exhibited an initial ageing effect. Once aged, glass-coated NaCoO2 showed the properties of a reliable counter electrode, i.e., rapid warm-up characteristics and a reproducible stationary potential at 450°C.
|Number of pages||6|
|Publication status||Published - 2004|
All Science Journal Classification (ASJC) codes
- Ceramics and Composites