Functionally graded cathodes based on double perovskite type GdBaCo2O5+δ oxide

• Functionally graded cathodes based on GdBaCo2O5+δ oxide were prepared.
• The cathode consists of an electrochemical active layer and a high conductive layer.
• The cathode shows improved electrochemical performance and high thermal stability.

Large thermal mismatch between GdBaCo2O5+δ (GBCO) oxide and solid electrolytes remains a challenge for its application as a cathode of solid oxide fuel cells (SOFCs). To avoid sharp discontinuities in composition, a functionally graded GBCO cathode is developed, which consists of an inner layer with high electrochemical activity and good thermal compatibility to electrolyte, and an outer layer with high electrical conductivity for current collection. Impedance spectra results reveal that the graded GBCO cathode shows a reduced polarization resistance and more importantly, an improved thermal stability during thermal cycling test. The present work confirms the advantage of graded GBCO cathode that is more robust and reliable for practical application.