Enhanced Oxygen Electrocatalysis in Heterostructured Ceria Electrolytes for Intermediate-Temperature Solid Oxide Fuel Cells

Heterostructured composite ceria electrolytes have been shown to accelerate the oxygen reduction activity and provide a new approach to improve solid oxide fuel cell (SOFC) performance. In this study, barium carbonate was added to gadolinium-doped ceria, Gd 0.2 Ce 0.8 O 2-δ (GDC) electrolyte to improve the electrochemical performance of intermediate-temperature SOFCs. The heterostructured electrolyte was formed by the addition of 5 wt % BaCO 3 to a GDC electrolyte, resulting in a reaction during sintering that formed well-dispersed BaCe 0.8 Gd 0.2 O 3-δ (BCG) throughout the electrolyte. The resulting material was tested as an electrolyte using La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ as a cathode, resulting in a dramatic reduction to the polarization resistance of more than half the value (600 and 700 °C, the resistance was reduced from 2.49 and 0.23 Ω cm 2 to 1.21 and 0.12 Ω cm 2 ) obtained by using pure GDC as an electrolyte. Furthermore, full cell SOFC tests employing the heterostructured electrolyte conducted during overextended durations indicated that the BCG phase in the 5BCG-GDC electrolyte was stable in an air atmosphere with no observed reactions with residual CO 2 . This approach of tailoring surface reactivity by tailoring the composition and structure of the electrolyte as opposed to electrode materials provides an alternative method to improve fuel cell performance.