Application of a Triple-Conducting Heterostructure Electrolyte of Ba_0.5Sr_0.5Co_0.1Fe_0.7Zr_0.1Y_0.1O_3−δ and Ca_0.04Ce_0.80Sm_0.16O_2−δ in a High-Performance Low-Temperature Solid Oxide Fuel Cell

Abstract

Dual-ion electrolytes with oxygen ion and proton-conducting properties are among the innovative solid oxide electrolytes, which exhibit a low Ohmic resistance at temperatures below 550 °C. BaCo_0.4Fe_0.4Zr_0.1Y_0.1O_3-δ with a perovskite-phase cathode has demonstrated efficient triple-charge conduction (H⁺/O^2-/e^-) in a high-performance low-temperature solid oxide fuel cell (LT-SOFC). Here, we designed another type of triple-charge conducting perovskite oxide based on Ba_0.5Sr_0.5Co_0.1Fe_0.7Zr_0.1Y_0.1O_3-δ (BSCFZY), which formed a heterostructure with ionic conductor Ca_0.04Ce_0.80Sm_0.16O_2-δ (SCDC), showing both a high ionic conductivity of 0.22 S cm^-1 and an excellent power output of 900 mW cm^-2 in a hybrid-ion LT-SOFC. In addition to demonstrating that a heterostructure BSCFZY-SCDC can be a good functional electrolyte, the existence of hybrid H⁺/O^2- conducting species in BSCFZY-SCDC was confirmed. The heterointerface formation between BSCFZY and SCDC can be explained by energy band alignment, which was verified through UV-vis spectroscopy and UV photoelectron spectroscopy (UPS). The interface may help in providing a pathway to enhance the ionic conductivities and to avoid short-circuiting. Various characterization techniques are used to probe the electrochemical and physical properties of the material containing dual-ion characteristics. The results indicate that the triple-charge conducting electrolyte is a potential candidate to further reduce the operating temperature of SOFC while simultaneously maintaining high performance.