Enhancing Sr-deficient Sr(Ti_0.3Fe_0.7)O_3–δ Cathode Performance through Sm_0.5Sr_0.5CoO_3–δ Infiltration

Abstract

The development of cathodes with improved polarization, aimed at reducing the operating temperature of solid oxide fuel cells (SOFCs), is an important avenue of research toward more efficient SOFCs. Sr(Ti0.3Fe0.7)O3–δ recently emerged as an active and stable cathode material; although its oxygen transport capability was shown to be further improved by introducing a Sr deficiency, the accompanying increased sinterability creates challenges in optimizing cathode microstructure. One facile approach may be single-step infiltration with highly active materials, such as Sr0.5Sm0.5CoO3–δ (SSC). However, there is limited knowledge regarding the impact of SSC on the electrochemical mechanisms within Sr-deficient Sr(Ti0.3Fe0.7)O3–δ. In this study, we systematically investigate the electrochemical characteristics of SSC-infiltrated Sr0.95(Ti0.3Fe0.7)O3–δ (STF) cathodes. Transmission line model-based impedance analysis provides a mechanistic understanding of STF and the role of SSC infiltrants in polarization improvement. The results reveal that SSC effectively reduces the resistance associated with key electrode processes, including oxygen diffusion, surface exchange, and dissociative adsorption/desorption. Consequently, using SSC infiltration, the power density of a Ni–Zr0.84Y0.16O2–δ (YSZ) anode-supported full cell with thin (~2.5 μm) electrolyte increased from ~1.88 to ~2.47 W cm–2 at 800 °C.