Transport features in layered nickelates: correlation between structure, oxygen diffusion, electrical and electrochemical properties
Résumé
Oxygen migration is increasingly acknowledged as playing an important role in the ionic transport in mixed conductors and influencing the electrode electrochemical performance. The aim of this work was to establish correlations between the structural and electrical properties of undoped (Ln2NiO4 + δ, Ln = La, Pr) and doped (La1.7M0.3NiO4 + δ, M = Ca, Sr, Ba, La0.85Pr0.85Ca0.3NiO4 + δ, Pr1.7Ca0.3NiO4 + δ) layered nickelates and the oxygen diffusion in these materials to determine what influences their electrochemical response. A new technique for temperature programmed isotope exchange of oxides with C18O2 in a flow reactor was applied to investigate oxygen mobility and surface reactivity in the polycrystalline powder samples which provided the means to experimentally demonstrate the appearance of two channels of oxygen migration in the doped materials via cooperative mechanism and via near-dopant position. The electrochemical performance of the electrodes based on the developed materials was found to exhibit a strong dependence on their oxygen transport characteristics.