Optimizing cathode materials for intermediate-temperature solid oxide fuel cells (SOFCs): Oxygen reduction on nanostructured lanthanum nickelate oxides

Kinetics of high temperature oxygen reduction reaction (ORR) on La2NiO4+delta (LNO) nanostructures are investigated by means of electrochemical impedance spectroscopy, with the aim of determining (i) the critical steps that govern ORR in these catalysts, and (ii) ways to lower the overpotential losses associated with these steps. We have identified two main electrochemical processes that govern the polarization resistances during ORR: the electron transfer/oxygen vacancy healing (O-ads + 2e(-) + V-(sic) double left right arrow O-o((LNO))X), and the oxygen ion transfer through the electrocatalyst/electrolyte interface (O-o(LNO)(X) + V-(sic) double left right arrow O-o(YSZ)(X)). find that the nanostructure of LNO significantly effects the activation barriers associated with these processes with nanorod-structured LNO catalyst, highly terminated by [001] surface facets, exhibiting lower barriers compared to traditional, spherical-shaped catalysts. We also show that incorporation of the nanorod-structured LNO as cathode electrocatalysts in SOFCs leads to a significant improvement in the cell performance. These findings provide important insights on the electrochemical steps that govern ORR kinetics on LNO electrocatalyst, and ways to optimize these materials as cathode electrocatalysts for intermediate temperature SOFCs (IT-SOFCs). 2016 Elsevier B.V. All rights reserved.