A CO 2 -Tolerant Perovskite Oxide with High Oxide Ion and Electronic Conductivity.

Mixed ionic-electronic conductors (MIECs) that display high oxide ion conductivity (σ _o ) and electronic conductivity (σ _e ) constitute an important family of electrocatalysts for a variety of applications including fuel cells and oxygen separation membranes. Often MIECs exhibit sufficient σ _e but inadequate σ _o . It has been a long-standing challenge to develop MIECs with both high σ _o and stability under device operation conditions. For example, the well-known perovskite oxide Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _{3- δ} (BSCF) exhibits exceptional σ _o and electrocatalytic activity. The reactivity of BSCF with CO ₂ , however, limits its use in practical applications. Here, the perovskite oxide Bi _0.15 Sr _0.85 Co _0.8 Fe _0.2 O _{3- δ} (BiSCF) is shown to exhibit not only exceptional bulk transport properties, with a σ _o among the highest for known MIECs, but also high CO ₂ tolerance. When used as an oxygen separation membrane, BiSCF displays high oxygen permeability comparable to that of BSCF and much higher stability under CO ₂ . The combination of high oxide transport properties and CO ₂ tolerance in a single-phase MIEC gives BiSCF a significant advantage over existing MIECs for practical applications.
(© 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)