Effects of Ceria on the Oxygen Reduction Activity and Thermal Cycling Stability of BaCo0.4Fe0.4Zr0.1Y0.1O3−δ Cathode for Solid Oxide Fuel Cells

Abstract

BaCo0.4Fe0.4Zr0.1Y0.1O3−δ (BCFZY) has been demonstrated to be a highly active yet large thermal expansion cathode catalyst for solid oxide fuel cells (SOFCs). In this work, gadolinia doped ceria (GDC) was mixed with BCFZY (BCFZY-GDC) to investigate its oxygen reduction reaction activities and chemical/thermal compatibility with electrolyte. Improved thermal compatibility of BCFZY-GDC with electrolyte and cathodic activity in symmetric cells were obtained, while, in contrast to the results of the common composite approach, the addition of ceria reduced surface exchange and bulk diffusion coefficient and subsequently decreased electrochemical performance under typical fuel cell condition. This interesting phenomenon was explored based on the limited electronic conductivity and using distinct modes of action of measurement techniques. Besides, SOFCs with BCFZY-GDC showed remarkable stability in 100 h of testing, during which 54 times of thermal cycling operations at 600–800 °C with a ramp rate of 20 °C min–1 were performed, whereas SOFCs using BCFZY showed gradually reduced performance in 9 times of thermal cycling and failed within 20 h of testing under the same operational condition, highlighting the crucial role of thermal compatibility among SOFC key components for efficient and durable energy conversion in practical application.