The effects of sintering temperature and current contacting layer on the performance of lanthanum nickelate electrodes in Solid Oxide Fuel Cells

The Ruddlesden-Popper phase La₂NiO_4+δ (LNO214) has received a significant level of research attention with respect to its employment as a Solid Oxide Fuel Cell cathode material. However, it is known that there are many factors that are capable of influencing the performance of this phase when utilised in this role. One such factor that can impact on electrode behaviour is the choice of sintering temperature. In this paper, a study of this effect is detailed. This is achieved via the use of both symmetrical and single cell testing configurations, with additional investigation provided by ex-situ analysis. It is shown that a sizeable improvement in electrode performance can be achieved via an increase in sintering temperature. This is despite observations on the reactivity between LNO214 and the contact electrolyte material Ce_0.9Gd_0.1O_2-δ. Further, it is also demonstrated that the addition of a noble metal contacting layer can dramatically improve the performance of an LNO214 electrode. In comparison, the impact of a contacting layer on a state-of-the-art La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ composition is shown to be relatively minor. This has implications towards SOFC testing methodologies given the widespread employment of noble metal contacting pastes.