Interlayer effects on oxygen reduction kinetics in porous electrodes of La_0.5Sr_0.5CoO_3-λ

Thick La_0.5Sr_0.5CoO_3-λ (LSCO) cathodes (∼30 [im) have been successfully fabricated with and without nanoporous LSCO interlayers on both sides of a dense polycrystalline gadolinia-doped ceria (CGO) substrate by combining screen printing and pulsed laser deposition (PLD) methods. The electrochemical properties of these LSCO cathodes for oxygen reduction reaction have been determined by electrochemical impedance spectroscopy (EIS) at different interlayer thicknesses, temperatures, and oxygen partial pressures. The oxygen reduction reaction on the LSCO electrode with and without the interlayer has been found to be mainly limited by the surface exchange process. By fitting the power density data by Butler-Volmer equation, it demonstrates that as the thickness of the PLD interlayer increases, the surface exchange resistance of the cathode decreases due to a significant increase in the number of reaction sites obtained by inserting the nanoporous LSCO interlayer.