Controlling surface cation segregation in a double perovskite for oxygen anion transport in high temperature energy conversion devices

• Published in: Physical chemistry chemical physics : PCCP 2023-08, Vol.25 (33), p.2222-2231
• Main Authors: Kala, Jyotsana, Anjum, Uzma, Mani, B. K, Haider, M. Ali
• Format: Article
• Language: English
• Subjects: Air batteries; Cations; Compressive properties; Density functional theory; Dopants; Energy conversion; High temperature; Ion migration; Molecular dynamics; Oxygen; Perovskites; Solid oxide fuel cells; Surface layers
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d3cp00827d

Double perovskite materials have shown promising applications as an electrode in solid oxide fuel cells and Li-air batteries for oxygen reduction, evolution, and transport. However, degradation of the material due to cation migration to the surface, forming secondary phases, poses an existential bottleneck in materials development. Herein, a theoretical approach combining density functional theory and molecular dynamics simulations is presented to study the Ba-cation segregation in a double perovskite NdBaCo 2 O 5+ δ . Solutions to circumvent segregation at the molecular level are presented in two different forms by applying strain and introducing dopants in the structure. On applying compressive strain or Ca as a dopant in the NBCO structure, segregation is estimated to reduce significantly. A more direct way of estimating cation segregation is proposed in MD simulations, wherein the counting of the cations migrating from the sub-surface layers to the surface provided a reliable theoretical assessment of the level of cation segregation. Doping at the A'-site and strain mediated strategies are proposed to suppress the degrading surface cation segregation in NdBaCo 2 O 5+ δ . A descriptor, degree of cation segregation, is proposed to provide more reliable estimation of cation segregation.