Mixed-potential gas sensor with PtAu-8YSZ sensing electrode: Electric potential difference measurements at isothermal and thermo-cyclic operation

A commercial mixed-potential gas sensor comprised of a pair of PtAu-YSZ sensing electrodes and a Pt-reference electrode was investigated at isothermal and thermo-cyclic operation under exposure to H2, CO and C3H6 balanced with synthetic air, separately. The sensor showed logarithmic response behavior to the variation of model gas concentration at isothermal operation and strong dependence on temperature. For the first time temperature dependent dynamic response behavior of the sensor was studied by cyclic triangular variation of the operating temperature at a period of 300s in a temperature range between 410°C and 670°C. The electric potential difference (delta V) measurements at thermo-cyclic condition revealed clearly distinct delta V-temperature profiles (ΔVTPs) depending on gas species and remarkable differences between the thermo-cyclic data and the corresponding delta V-values measured at isothermal conditions. Moreover, it was found out that the stability and reversibility of ΔVTPs depends on sensor operating temperature and is a specific characteristic of the individual gas component as well.