Development of La 1.7 Ca 0.3 Ni 1-y Cu y O 4+δ Materials for Oxygen Permeation Membranes and Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells.

The La 1.7 Ca 0.3 Ni 1-y Cu y O 4+δ (y = 0.0-0.4) nickelates, synthesized via a solid-state reaction method, are investigated as prospective materials for oxygen permeation membranes and IT-SOFC cathodes. The obtained oxides are single-phase and possess a tetragonal structure ( I4 / mmm sp. gr.). The unit cell parameter c and the cell volume increase with Cu-substitution. The interstitial oxygen content and total conductivity decrease with Cu-substitution. The low concentration of mobile interstitial oxygen ions results in a limited oxygen permeability of Cu-substituted La 1.7 Ca 0.3 NiO 4+δ ceramic membranes. However, increasing the Cu content over y = 0.2 induces two beneficial effects: enhancement of the electrochemical activity of the La 1.7 Ca 0.3 Ni 1-y Cu y O 4+δ (y = 0.0; 0.2; 0.4) electrodes and decreasing the sintering temperature from 1200 °C to 900 °C. Enhanced electrode activity is due to better sintering properties of the developed materials ensuring excellent adhesion and facilitating the charge transfer at the electrode/electrolyte interface and, probably, faster oxygen exchange in Cu-rich materials. The polarization resistance of the La 1.7 Ca 0.3 Ni 1.6 Cu 0.4 O 4+δ electrode on the Ce 0.8 Sm 0.2 O 1.9 electrolyte is as low as 0.15 Ω cm 2 and 1.95 Ω cm 2 at 850 °C and 700 °C in air, respectively. The results of the present work demonstrate that the developed La 1.7 Ca 0.3 Ni 0.6 Cu 0.4 O 4+δ -based electrode can be considered as a potential cathode for intermediate-temperature solid oxide fuel cells.