Evaluating the Rate-determining Steps of Oxygen Permeation in Ba_0.5La_0.5FeO_3−δ Perovskite

Abstract

Perovskite oxides obtained from Ba_1−xLa_xFeO_3−δ (BLF) are considered beneficial materials for electrodes of solid oxide fuel cells and oxygen permeation membranes because of their high oxygen permeability, which is a criterion of oxide ion (O²⁻)-electronic mixed conductivity. In this paper, the prime focus was to understand the oxygen permeation mechanism through surface exchange and bulk diffusion of the Ba_0.5La_0.5FeO_3−δ (BLF55) sample. The permeated oxygen flux displayed higher than that of the typical mixed conductor La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF), which was explored simultaneously with corresponding oxygen chemical potentials employing an especial experimental setup. This study found that the surface exchange reaction on the oxygen-lean side was the rate-determining step (RDS) of the oxygen permeation below 800 °C, resulting from lower hole concentration on the oxygen-lean side surface. Enhancing the charge transfer from the surface oxygen by increasing hole concentration is a prime important strategy to improve the surface exchange reaction.