High-performance La0.5Ba0.5Co1/3Mn1/3Fe1/3O3-δ – BaZr1-zYzO3-δ cathode composites via exsolution mechanism for protonic ceramic fuel cells

Abstract

A novel exsolution process was used to fabricate complex all-oxide nanocomposite cathodes for protonic ceramic fuel cells (PCFCs). The nanocomposite cathodes with La0.5Ba0.5Co1/3Mn1/3Fe1/3O3-δ – BaZr1-zYzO3-δ nominal composition were prepared from a single phase precursor via an oxidation driven exsolution mechanism. The exsolution process results in a highly nanostructured and intimately interconnected percolating network of the two final phases, one proton conducting (BaZr1-zYzO3-δ) and one mixed oxygen ion and electron conducting (La0.5Ba0.5Co1/3Mn1/3Fe1/3O3-δ), yielding excellent cathode performance. The cathode powder is synthesized as single phase cubic precursor by a modified Pechini route followed by annealing at 700 °C in N2. The precursor phase is exsolved into two cubic perovskite phases by further heat treatment in air. The phase composition and chemical composition of the two phases were confirmed by Rietveld refinement. The electrical conductivity of the composites was measured and the electrochemical performance was determined by impedance spectroscopy of symmetrical cells using BaZr0.9Y0.1O2.95 as electrolyte. Our results establish the potential of this exsolution method where a large number of different cations can be used to design composite cathodes. La0.5Ba0.5Co1/3Mn1/3Fe1/3O3-δ - BaZr0.9Y0.1O2.95 composite cathode shows the best performance of 0.44 Ω∙cm2 at 600 °C in 3 % moist synthetic air.