Investigation of the effect of off-stoichiometric composition on oxygen transport in layered perovskite materials for SOFC cathode

Abstract

Layered perovskite materials are of significant interest for potential use as cathodes in solid oxide fuel cells. This study employs deep-learning-aided molecular dynamics simulations to investigate the impact of off-stoichiometric composition in praseodymium barium cobalt oxide and samarium barium cobalt oxide on O-ion transport properties. It is observed that increasing the deficiency of lanthanide-site atoms while suppressing the formation of O vacancies enhances O-ion mobility. This finding suggests adjusting synthetic conditions to achieve this state by controlling the design composition and heating atmosphere. The underlying mechanisms for the simulation results are explored, including the migration energy barrier of O ions, Co’s oxidation state change, and alterations in crystal structure, which indicate that structural changes and secondary phase formation are closely linked to O-ion mobility. Ba and Co infiltrate vacant lanthanide sites in the crystals under conditions of high lanthanide site deficiency and low O vacancy concentrations, promoting the formation of secondary phases composed of Ba, Co, and O, thereby creating favorable conditions for O-ion migration.