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

By Carneiro, Juliana Silva Alves; Brocca, Roger Antunes; Lucena, Max Laylson Ribeiro Sampaio; Nikolla, Eranda
Published in Applied Catalysis B: Environmental NULL 2017

Abstract

Abstract Kinetics of high temperature oxygen reduction reaction (ORR) on La2NiO4 + ? (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 a d s + 2 e ? + V O ? ? ? O O ( L N O ) X ) , and the oxygen ion transfer through the electrocatalyst/electrolyte interface ( O O ( L N O ) X + V O ? ? ? O O ( Y S Z ) X ) . We 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).

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