Electrochemical Characterization of NdBa0.9Co2O5+δ SOFC Cathodes Prepared by Infiltration into Gd Doped Ceria Scaffolds

Abstract

In this work, the electrocatalytic properties of novel cathodes prepared by infiltration of NdBa0.9Co2O5+δ (NBC) into porous Gd doped Ceria (GDC) scaffolds are investigated, and comparison is provided with La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) infiltrated GDC cathodes. For both formulations, symmetric cells are fabricated by blade coating and infiltration of aqueous nitrate precursor solutions until reaching 25% w/w load. The effects of the calcination temperature are explored between 750 °C and 950 °C for the NBC-GDC cathodes. Electrochemical impedance spectroscopy and polarization experiments are performed to study the electrocatalytic activity in the oxygen reduction reaction. Compared to LSCF-GDC, a remarkable improvement of the polarization resistance is found on the best performing NBC-GDC cathode between 500 °C and 700 °C (0.022 Ω cm2 vs 0.1 Ω cm2 at 700 °C). A shift in the rate determining step characterizes the performance of the NBC-GDC cathode above 650 °C, wherein the interfacial oxide ion transfer resistance prevails, while below 650 °C the surface exchange resistance dominates. Different stability behaviors are observed in ageing experiments up to 200 h: the NBC-GDC electrodes show constant ohmic resistance and moderate improvement of the polarization resistance at 700 °C and 550 °C, while the LSCF-GDC electrodes experience degradation.