Self-assembled La0.6Sr0.4FeO3-δ-La1.2Sr0.8NiO4+δ composite cathode for protonic ceramic fuel cells

Abstract

The oxygen reduction reaction at the cathode is an essential process for protonic ceramic fuel cells. Composite cathode materials are commonly used towards the multiple requirements including high surface oxygen activity as well as sufficient electronic and ionic conductivities. In this study, a cobalt-free composite cathode composed of a perovskite La0.6Sr0.4FeO3-δ phase and a Ruddlesden-Popper La1.2Sr0.8NiO4+δ phase is synthesized with a self-assembly technology. The cathode process is mainly controlled by (I) the reduction of adsorbed oxygen atom to O− on the surface and (II) the migration of O− from the surface into the lattice. The former benefits from the high electrical conductivity of La0.6Sr0.4FeO3-δ, and the latter is accelerated by La1.2Sr0.8NiO4+δ attributed to its superior oxygen activity. The one-pot synthesized composite cathode shows an enhanced synergistic effect due to the uniform distribution of the two phases at the nanoscale. The cathode shows the lowest polarization resistances of 0.055 and 0.095 Ω cm2 at 700 °C in oxygen and air, respectively. The results show that self-assembled La0.6Sr0.4FeO3-δ-La1.2Sr0.8NiO4+δ nanocomposite is a promising cathode material for protonic ceramic fuel cells.