Ni-free CeO2-ZrO2-Sc2O3 nanostructured fuel electrodes for high performance solid oxide cells

Abstract

Ni-based state-of-the-art cermet electrodes for SOFC are prone to deactivation when using hydrocarbon-based fuels due to surface carbon deposition. CeO2-based oxides offer major advantages to improve long-term performance of electrodes, such as high oxygen transport properties, carbon deposition resistance and optimum chemical compatibility with intermediate temperature SOFC (IT-SOFC) high performance electrolytes. Ceria-containing electrodes are generally mixed with Ni or other metallic phases to improve electronic percolation. In this work, we present two Ni-free electrodes: Ce0.9Zr0.1O2-δ and Ce0.9Zr0.06Sc0.04O2-δ. These electrodes exhibit a large amount of electrochemical reaction sites due to the nanoscale particle size distribution of the electrode material (Dav=25 nm). We show that, by partially replacing Zr by Sc in the Ce0.9Zr0.1O2 lattice, the polarization resistance of the electrode is significantly improved. The Sc-containing system exhibited a superior performance especially when using CH4 as fuel, thus implying that the incorporation of additional oxygen vacancies in the lattice enhances the electrode activity for fuel oxidation and its resistance towards carbon formation. These results reveal that the Ce0.9Zr0.06Sc0.04O2-δ electrode stands both as a promising Ni-free anode for IT-SOFC/SOEC operation and as a highly active redox support for Ni-based cermets.