| Popis: |
The CO, O 2 , PtAu/ZrO 2 (0.92)Y 2 O 3 (0.04)Yb 2 O 3 (0.04)/Pt, air system has been recently proposed as CO, O 2 sensor. Thermodynamic measurements of the open-circuit potential, E 0 , of the interphase CO, O 2 , PtAu/ZrO 2 (0.92)Y 2 O 3 (0.04)Yb 2 O 3 (0.04) as a function of the carbon monoxide/oxygen pressure ratio were carried out at T = 773 K and T = 873 K and confirmed the recently obtained results that the cell operates as a reproducible and CO-sensitive sensor. To clarify whether the carbon monoxide takes part in an electrochemical reaction step or is oxidized only in a chemical step, i.e. in a heterogenous catalytic reaction, dynamic measurements using electrochemical impedance spectroscopy (EIS) were performed. They show a mixed charge transfer and transport controlled kinetic behavior. The polarization resistance, R p , decreases with increasing P CO / P O2 ratio at constant P O2 . This clearly indicates an electrochemical step of carbon monoxide oxidation in the overall reaction in agreement with previous results obtained for pure platinum paint electrodes. |
