Evolution of elemental distribution in single liquid precursor-derived nanocomposite solid oxide cell electrodes at nanoscale and its impact on electrochemical performance stability

Abstract

A powder-free solid oxide cell electrode fabrication route is demonstrated, in which a polymeric precursor, containing the cations of electrocatalyst and ionic conductor phases, is deposited onto a dense electrolyte. By this approach, the formation of a La0.8Sr0.2FeO3-Ce0.8Sm0.2O2 (LSF-SDC) nanocomposite structure because of nanoscale phase separation was ensured upon drying by low-temperature heat treatment. The long-term stability of their electrochemical performance was tracked and correlated with the evolution of the elemental distribution at the nanoscale via electrochemical impedance spectroscopy and detailed electron microscopy/x-ray spectroscopy, respectively. The nanocomposite structure yielded electrode polarization resistances as low as 0.34 Omega center dot cm(2) at 650 degrees C. Long-term performance stability is shown to be determined by the pre-heat treatment step. Samples heat-treated at 800 degrees C underwent continuous performance degradation, driven by the de-mixing of a Sr-rich phase. By contrast, LSF-SDC electrodes that were not heat-treated did not undergo such a phase separation and exhibited stable electrochemical performance.