Heterostructured electrodes for Cr-tolerant solid oxide fuel cells

Abstract

Cr poisoning at the surface of Sr-doped perovskite oxides significantly reduces the durability of solid oxide fuel cells during stack operation under practical atmospheres. This poisoning is attributed to the interactions between vaporized Cr and segregated Sr at the surface, facilitated by the electrostatic interaction of oxygen vacancies and doped Sr. To address this issue, we designed a heterostructured electrode coated with a Cr-tolerant Sr-free material, which exhibits a low oxygen-vacancy concentration and contains reducible sites, preventing direct contact between vaporized Cr and Sr. By redistributing the charged defects near the heterointerface, excessive oxygen vacancies in the bulk electrode are reduced, leading to suppressed Sr segregation and Cr poisoning. Evaluation of thin-film model electrodes reveals significantly improved stability of the heterostructured electrode in both ambient air and a Cr atmosphere at 600 °C for 100 h as well as its enhanced oxygen reduction reaction kinetics. Furthermore, we demonstrate the feasibility of using this approach to fabricate a porous electrode, exhibiting high performance and high stability with nearly no degradation at 600 °C for 300 h. This paper presents a rational design strategy for Cr-tolerant hetero-structured electrodes, particularly based on Sr-doped perovskite oxides, considering physical, chemical, and electrochemical stabilities and performances.