Investigation of in Situ Co-assembled Sr(Co,Zr)O3−δ-Based Perovskite Nanocomposite Cathode for Intermediate-Temperature Solid Oxide Fuel Cells

Abstract

Exploring cathode materials with fast oxygen reduction reaction (ORR) kinetics is crucial to intermediate-temperature solid oxide fuel cells (SOFCs). Herein, a highly active perovskite nanocomposite with a nominal composition of SrCo0.8Zr0.2O3−δ is developed. The two perovskite phases of cubic SrZr0.8Co0.2O3−δ (SZC, Pm3̅m, 30 wt %) and hexagonal SrCo0.9Zr0.1O3−δ (SCZ, R3̅cH, 70 wt %) can be in situ co-assembled at the nanoscale for well-connected nanoparticles (50–100 nm) and congenital compatibility. The SZC–SCZ nanocomposite can exhibit the active surface oxygen species and a matchable thermal expansion coefficient (15.3 × 10–6 K–1) with Ce0.8Gd0.2O1.9 (13.5 × 10–6 K–1) electrolyte. When applied to the anode-supported SOFC, SZC–SCZ nanocomposite cathode cell shows superior power densities of 1.48–0.41 W cm–2 at 750–550 °C to single cubic SZC cathode cell (0.24–0.06 W cm–2) and typical hexagonal SrCoO3−δ cathode cell (1.25–0.32 W cm–2). The distribution of relaxation times analysis reveals that the oxygen adsorption and dissociation process of SZC–SCZ nanocomposite cathode is significantly enhanced, of which the polarization resistances (0.07–0.22 Ω cm2) are 0.70–0.43 times those of SrCoO3−δ cathode. This benefits from the nanostructure for an extensive heterointerface and surface, and the synergistic interaction of components can contribute to enhancing oxygen catalysis. Thus, this work explores a promising SZC–SCZ nanocomposite cathode for enhancing ORR activity and cell performance at lower operating temperatures.