Optimization of La2NiO4 cathode for SOFC

The commercialisation of Solid Oxide Fuel Cells requires stable and cheap components. Although La0.6Sr0.4Co0.2Fe0.8O3-δ is an excellent cathode material, it suffers from Crpoisoning by the metallic CroFer interconnect, which has led to a search for Cr-resistant cathode materials. One of the possible candidates is La2NiO4 (LNO), a layered compound with high (2-D) ionic conductivity and high surface oxygen exchange rate. The influence of microstructure on the electrode properties are investigated with impedance spectroscopy. Addition of a dense LNO-layer by Pulsed Laser Deposition between electrolyte and the porous, screen printed LNO electrode significantly lowers the electrode polarisation. Interpretation of the impedance analysis indicates that the electronic resistance of the LNO-electrode is a performance limiting factor. It is also evident from the observation of a predominant Gerischer contribution to the impedance of the porous cathodes that surface diffusion of (possibly charged) oxygen species is the main oxygen transport mechanism. The cathode with the 800 nm LNO-PLD layer can be modelled with a previously developed model for a dense layer electrode where the oxygen exchange rate is modified by the porous LNO structure on top of the layer.