The effects of polarisation on the performance of the Ba2Co9O14–Ce0.8Gd0.2O2- composite electrode for fuel cells and electrolysers

Abstract

The potential of the [BaCoO3]n [BaCo8O11] family as a cathode for solid oxide fuel cells (SOFCs) or as an anode for solid oxide electrolyser cells (SOECs) is investigated via structural, microstructural and electrochemical characterisation. The crystallographic structure of the n = 1 member compound, Ba2Co9O14 (BCO), exhibits rhombohedral symmetry and presents a microstructure consisting of large platelets. Overall, the electrochemical performance of the Ba2Co9O14/Ce0.8Gd0.2O2-δ (BCO/CGO-20) composite electrode is found to be enhanced under cathodic polarisation, while becoming impaired under anodic polarisation. The latter behaviour may result from the high local oxygen partial pressures upon increasing the applied anodic polarisation that lead to a depletion of oxygen vacancies at the electrode/electrolyte interface, thus, decreasing the ionic conductivity as well as electrocatalytic activity of this interface. This work, therefore, provides the first electrochemical analysis of the performance of BCO-based electrodes under applied polarisation conditions for SOFC and SOEC applications, and highlights the higher potential of this compound as a cathode material for intermediate-temperature solid oxide fuel cells.