Experiencing heightened oxygen reduction response in CaFe2O4-WO3 heterostructure for ceramic fuel cells

A fundamental understanding of oxygen reduction reaction (ORR) is essential for low-temperature solid oxide fuel cells (LT-SOFCs). In this work, following our previous studies of protonic ceramic fuel cell (PCFCs) cathode material, CaFe2O4-WO3 heterostructure composite material is used as an air electrode over oxide ion conducting electrolyte ceramic fuel cell. CaFe2O4-WO3 as a cathode over Sm-doped CeO2 (SDC) electrolyte exhibits a very low area-specific resistance (ASR) of 0.18 Ω cm2 and excellent power output of 842 mW-cm−2 at 500 °C. The CaFe2O4-WO3 cathode showed improved electrochemical performance in LT-SOFC compared to PCFCs [1]. The excellent ORR activity of CaFe2O4-WO3 could mainly be assisted with the superficial release of oxygen ions than the protons with enhanced incorporation abilities through the interface of CaFe2O4-WO3 heterostructure. Moreover, engineering the heterostructure by forming complex oxidation states at the interface of CaFe2O4-WO3 narrows the band gap. It can effectively facilitate small polaron hopping of valence electrons and diffusion of oxygen ions, resulting in high electrical conductivity and electrocatalyst function in SOFCs. In addition, various spectroscopic and density functional calculations are employed to catch the understanding of CaFe2O4-WO3 heterostructure composite as a new functional ORR electrocatalysts for advanced LT-SOFCs.