Effects of voltage variations in pulsed polarization measurements

Title data

Donker, Nils ; Ruchets, Anastasiya ; Schönauer-Kamin, Daniela ; Zosel, Jens ; Guth, Ulrich ; Moos, Ralf:
Effects of voltage variations in pulsed polarization measurements.
2019
Event: 2nd Cross-Border Seminar on Electroanalytical Chemistry (CBSEC) , 10.4.-12.4.2019 , Budweis.
(Conference item: Conference , Speech )

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Abstract in another language

Most sensors for nitrogen oxides (NOx; NO and NO2) are based on potentiometric (equilibrium and non-equilibrium), amperometric, or impedancemetric principles to detect the concentration of NOx in the atmosphere. All these methods have in common that they reach a steady state value at a constant atmosphere after certain time. In contrast, the pulsed polarization method is a dynamic method and it utilizes the well-known Pt|YSZ-system. Platinum electrodes are screen printed on both sides of a YSZ substrate for this purpose. Both sensor electrodes are exposed to the same gas atmosphere at the same temperature. Therefore, a potentiometric measurement would result in the voltage difference 0 V. For pulsed polarization, the sensor is polarized with the voltage Upol for a defined duration tpol. Next, the sensor self-discharges after the voltage source has been removed (open circuit conditions). It could be shown, that the self-discharge accelerates strongly with increasing NOx concentration. After the discharge time tdischarge, the sensor is polarized again for the duration tpol, but with the opposite sign -Upol. A sensor signal can be generated by using the sensor voltage at a defined point in time during depolarisation. Since the self-discharge is accelerated by NO, this voltage value is lower in the presence of nitrogen oxides. In this study, the operation of the pulse polarization with different polarization voltages shall be shown. It is to be expected that different processes will occur at the Pt|YSZ system depending on the voltage applied. For example, the literature mentions oxide formation at the Pt|YSZ interface, which could lead to a different self-discharge and thus to different sensor signals.