A CO₂‐Tolerant Perovskite Oxide with High Oxide Ion and Electronic Conductivity

Abstract

Abstract 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.