LnBaCo[sub 2]O[sub 5+δ] Oxides as Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells

TLDR

LnBaCo₂O₅+δ oxides with a cation‑ordered perovskite structure are studied as intermediate‑temperature SOFC cathodes, and their oxygen content, thermal expansion, and metallic conductivity all decline as the lanthanide ionic radius shrinks from La to Y due to reduced ionicity, increased oxide vacancies, and O–Co–O bond bending. Single‑cell SOFCs with these cathodes show lower power density as the lanthanide ion size decreases, while intermediate‑size lanthanides provide a balance between catalytic activity and thermal expansion.

Abstract

, Sm, Gd, and Y) oxides with a cation ordered perovskite structure have been investigated as cathode materials for intermediate-temperature solid oxide fuel cells (SOFCs). The oxygen content , thermal expansion coefficient (TEC), and electrical conductivity (metallic) decrease with decreasing size of the ions from to Y. While the decrease in TEC is due to the decreasing ionicity of the Ln–O bond, the decrease in electrical conductivity is due to the increasing oxide ion vacancies and a bending of the O–Co–O bonds. The power density of single-cell SOFCs fabricated with the cathodes, electrolyte, and cermet anode decrease with decreasing size of the ions, partly due to a decreasing electrical conductivity. The cathodes with an intermediate lanthanide ion such as offer a trade-off between catalytic activity and TEC.