Microstructural dependent oxygen reduction reaction in a Ruddlesden–Popper perovskite (SmSr)NiO4−δ†
Rare earth nickelate perovskites have very wide uses, as magnetic insulators, as well as being conducting materials for the various components of solid oxide fuel cells (SOFCs) due to them undergoing an insulator to metal transition below operating temperature. In SOFCs, the microstructural design of electrode materials is an important aspect for electron and oxygen ion conduction at the electrolyte–electrode and electrode–air interfaces. To investigate this feature, a Ruddlesen–Popper structured layered perovskite, (SmSr)NiO4−δ, was synthesized at different sintering temperatures using a solid-state reaction technique. Porous and dense microstructures were obtained at sintering temperatures of 1250 and 1425 °C, respectively. The influence of electrocatalysis on the structures of both surfaces was studied comprehensively. Post cyclic voltammetry structural studies show the presence of Ni–(OH)2 and Ni–OOH species for the samples, respectively, suggesting that they undergo different oxygen reduction reaction mechanisms.