Investigation of La2 Cu O4 YSZPt potentiometric N Ox sensors with electrochemical impedance spectroscopy

La2 Cu O4 (LCO) powders were used to fabricate electrodes for solid-state potentiometric N Ox sensors [LCO∫yttria-stabilized zirconia (YSZ)∫Pt], and symmetrical Pt (Pt∫YSZ∫Pt) and La2 Cu O4 (LCO∫YSZ∫LCO) cells. The impedances of the sensors and symmetrical cells were measured. Three phenomena were observed in the impedance spectra: O2 ion conduction in the YSZ electrolyte, surface conduction on the La2 Cu O4 electrode, and the electrochemical reaction of O2 at the electrode/electrolyte/gas interface. The impedance associated with O2 reduction/oxidation decreased in the presence of O2, NO, and N O2, in contrast to the potentiometric response which increased in NO, decreased in N O2, and was unaffected by changes in O2 concentration. The impedance associated with surface conduction on the La2 Cu O4 electrode was affected by NO and N O2 in much the same way as the previously reported potentiometric sensor response (ΔOCP) in terms of temperature and concentration dependencies providing evidence for an adsorption mechanism for the potentiometric response.