The Effects of Sintering Temperature and Current Contacting Layer on the Performance of Lanthanum Nickelate Electrodes in Solid Oxide Fuel Cells

Abstract

The Ruddlesden-Popper phase La2NiO4+δ (LNO214) has received a significant level of research attention with respect to its employment as a Solid Oxide Fuel Cell cathode material. Significantly, this phase offers excellent oxygen transport properties which results from a facile interstitial oxide migration through its crystal structure. In addition, and most significantly, the lanthanum nickelates are commonly thought to offer resilience to the effects of chromium poisoning, which has been shown to be a source of significant degradation in other materials.  As a result of these factors, many researchers have looked to adopt La2NiO4+δ as an air electrode material, with a view to replacing the more conventional lanthanum cobaltite-type perovskites that are found in the state-of-the-art commercial cells and stacks. Many authors across a number of research groups have demonstrated very wide variations in electrode performance behaviours with the La2NiO4+δ phase employed as a cathode material. This likely results from differences in cell materials, fabrication routes, and testing approaches. One factor that is of interest in relation to this material is the effect of sintering temperatures on the resulting electrode performance. Several observations can be made in the literature. On the one hand, there is evidence to indicate a detrimental reactivity with electrolyte phases and, on the other, some authors have commented on the need to employ higher temperature sintering conditions to achieve electrodes with suitable adherence to the electrolyte. In this paper, an attempt at providing a more comprehensive understanding of the performance of LNO214 electrodes in symmetrical and single cell testing configurations is offered. As a result of increasing sintering temperatures, a sizeable improvement in electrode performance has been found to be possible. Further, the addition of a noble metal contacting layer was shown to dramatically improve the electrode performance due to improvements in the electronic conductivity.

Keywords: Solid Oxide Fuel Cell, SOFC, cathode, La2NiO4+δ, sintering temperature