Multi-phase La-Sr-Co-O fuel cell cathode materials and influence of phase boundaries on oxygen exchange activity

Abstract

The present work deals with the investigation of dense pulsed laser deposited (PLD) La-Sr-Co-O thin films which contain one or more perovskite related phases with catalytic activity for the oxygen reduction reaction (ORR). For the performance of solid oxide fuel cells (SOFC), a high ORR activity of the cathode material is decisive, in particular when attempting to lower the operation temperature. There are literature reports that enhanced ORR activities can be reached at hetero-interfaces of two different electronically and ionically conducting cathode materials, as demonstrated for (La,Sr)CoO3-d perovskite phase / (La,Sr)2CoO4+d Ruddlesden-Popper phase ("TPB effect", Kawada and Sase et al. 2006 and Crumlin et al. 2010). So far, no systematic experiments were performed to quantify the strength of the TPB effect (i.e. contribution of TPBs to ORR activity per TPB length). The present work therefore concentrated on the fundamental investigation of the TPB effect, a proper chemical and morphological characterization of the self-assembled La-Sr-Co-O composite cathode films containing perovskite and Ruddlesden-Popper phase and the quantification of the strength of the TPB effect.