Self-assembled nano-composite perovskites as highly efficient and robust hybrid cathodes for solid oxide fuel cells

Abstract

The oxygen reduction reaction, which proceeds at the cathode of a fuel cell, is primarily important as its rate determines the overall performance of a device. However, designing a single-phase material that meets multiple standards (e.g., high activity, stability, and thermomechanical characteristics) at once to become an ideal cathode still remains a great challenge. In this regard, the use of multi-phase catalysts, especially those with complex nanoscale domains, may serve as a rational strategy. Here, we present Ba_0.5Sr_0.5Co_0.6Fe_0.2Zr_0.1Y_0.1O_3−δ (BSCFZY) as a superior biphasic nano-composite cathode, which self-assembles into two discrete cubic perovskites: Co-rich (Ba_0.5Sr_0.5Co_0.7Fe_0.2Zr_0.07Y_0.03O_3−δ) and Zr-rich (Ba_0.6Sr_0.4Co_0.3Fe_0.2Zr_0.4Y_0.1O_3−δ) phases. The former promotes the electrocatalytic activity while the latter supports the microstructural robustness; thus, the synergic ensemble of Co- and Zr-rich perovskite domains yields an area specific resistance of only ∼0.013 Ω cm² at 650 °C, which is far superior to that anticipated from the component phases in isolation. The cooperative interaction found in multi-phase catalysts prepared via a simple one-pot synthesis is not only attractive for SOFCs but also for other kinds of energy conversion and storage devices, such as protonic ceramic electrochemical cells, electrolysers, and membrane chemical reformers.