Design of Active Site at Heterointerface between Brownmillerite Type Oxide Promoter and Fluorite Cubic ZrO2 in Anode of Intermediate Temperature SOFCs

New hopping site for mobile oxygen (i.e., active site) on cubic ZrO2 surface in the anode was designed along the guide of previously published first-principles simulation. To design it, the authors proposed a heterointerface between brownmillerite type oxide and fluorite type cubic ZrO2 ("BF heterointerface") as model active site. Small amount (0.2 wt %) of brownmillerite type oxide promoter made new hopping site on YSZ and conspicuously improved both anode performance and its stability at 700 degrees C. The combination work of XPS analysis and surface atomistic simulation suggests the formation of Frenkel type defect clusters on BF heterointerface. Also, this combination work was useful to conclude why the optimum content of brownmillerite type oxide for promotion of anode reaction was around 0.2 wt %. Finally, it is found that "BF heterointerface" designed by combination of the modeling, surface microanalysis, and fabrication can solve the trade-off relation between high anode performance and its long-time stability for development of state-of-the-art IT-SOFC.