This thesis deals with the rare earth nickelate La2NiO4+δ (LNO) in terms of its fundamental material properties, with a particular focus on oxygen exchange kinetics and electrochemical characterization relevant for potential application as oxygen electrode in solid oxide electrolysis cells (SOECs). The impact of partial substitution of nickel with 10 % cobalt is evaluated, as well as the effect of surface modification by acid etching with HNO3. The electronic conductivity and the chemical surface exchange coefficients are determined by dc conductivity relaxation measurements on a bar shaped sample. The substitution of nickel with cobalt in La2Ni0.9Co0.1O4+δ (LNCO291) leads to significantly higher surface exchange coefficients and a lower activation energy of the surface exchange reaction compared to LNO, while the electronic conductivity experiences a slight reduction. The conductivity relaxation measurements on the etched sample yield noteworthy results. The surface exchange coefficients of oxygen are increased and a further reduction in the activation energy compared to the unetched LNO and LNCO291 is achieved. It is observed that acid etching has no effect on the electrical conductivity. X ray photoelectron spectroscopy (XPS) is employed to obtain comprehensive data on the surface chemistry. The findings indicate the formation of a nickel depleted phase on the surface of the etched sample. Consequently, it can be inferred that La2O3 is the predominant phase on the surface.
Furthermore, the electrochemical properties of LNCO291 are examined through the use of current density-voltage (I-V) curves on an electrolyte supported cell. The substitution of nickel with 10 % cobalt results in a slight enhancement in cell performance, thereby indicating that LNCO291 shows promising properties for use as an oxygen electrode material in SOECs. The impact of nickel and lanthanum oxide infiltration on symmetrical cells is examined using electrochemical impedance spectroscopy (EIS). The results suggest that nickel infiltration enhances the cell performance, whereas lanthanum infiltration shows the opposite effect. Post-test analyses using scanning electron microscopy (SEM) are carried out to confirm the porous microstructure of the electrodes and to characterize the cross sections of the electrode electrolyte interfaces of the cells, which confirm good adhesion between the layers.