Impedance spectroscopy based characterization of an electrochemical propylene sensor

In this investigation, an electrochemical mixed potential type gas sensor was characterized using impedance spectroscopy. Specifically, the effect of operating temperature (435–610 °C) on sensor response and response time was studied. Propylene was used as the analyte to test the ‘La0.8Sr0.2CrO3/YSZ/Pt’ sensor configuration. Two-electrode AC impedance measurement was performed with a frequency sweep from 13 MHz down to 10 mHz and excitation voltage of 10 mV.For a fixed propylene concentration, the bulk and interfacial resistances was seen to decrease with increase in the sensor operating temperature. An Arrhenius behavior of the bulk and interfacial resistance was observed. The activation energy for O2 ion conduction and charge transfer was found to be 0.94 eV and 1.54 eV respectively. For a 150 °C rise in operating temperature from 485 to 585 °C, a 26-fold improvement in response rise time was observed while an 82% reduction in sensor response was recorded. It is postulated that the increase in operating temperature results in faster reaction kinetics, faster oxygen reduction and greater heterogeneous catalysis.