A kinetic study of oxygen reduction reaction on La2NiO4 cathodes by means of impedance spectroscopy

The oxygen reduction reaction has been investigated at the La2NiO4+δ/YSZ interface by impedance spectroscopy. The study has been performed in the temperature range 600–800 °C under different oxygen partial pressures under zero dc conditions. The analysis of the impedance diagrams revealed at least the presence of three processes involved in the reduction reaction. The first process at high-frequency was assigned to transport of oxide ions and/or oxygen intermediates within the electrode structure and the electrode/electrolyte interface. The second one at medium-frequency arc was associated to atomic oxygen diffusion within the electrode followed by a charge transfer. This is the rate limiting step in the overall oxygen reduction reaction at oxygen partial pressure ⩾0.2 atm and temperature >600 °C under zero dc conditions. Finally, the third arc at low-frequency could be related to molecular oxygen dissociation and adsorption phenomena. This last process disappears under 100% O2 and becomes more important at low oxygen partial pressure pO2 < 0.2 atm.