Role of silver current collector on the operational stability of selected cobalt-containing oxide electrodes for oxygen reduction reaction

The long-term stability for oxygen reduction reaction (ORR) of two typical perovskite cathode materials of SOFCs, i.e., Ba _0.5Sr _0.5Co _0.8Fe _0.2O _3-δ (BSCF) and Sm _0.5Sr _0.5CoO _3-δ (SSC), is investigated in a symmetric cell configuration under air condition at 700 °C using Sm _0.2Ce _0.8O _1.9 (SDC) electrolyte substrate and silver current collectors. Moreover, two different methods of silver current collection are tested, i.e., whole electrode surface deposited with a diluted silver paste (CC-01) and a mesh-like current collector using concentrated silver paste (CC-02). Electrochemical impedance spectra are applied for stability investigations. With the CC-01 current collector, the performance of the electrode deteriorates significantly, although the initial performance is good. By contrast, fairly stable performance is obtained from symmetric cells with either BSCF or SSC + SDC electrodes using the CC-02 current collector, even though a phase transition is observed for BSCF. For instance, after approximately 800 h of continuous stability testing, the area-specific resistance of the BSCF electrode retains a value of approximately 0.065 Ω cm ², except for a slight fluctuation within the range of 0.06-0.07 Ω cm ². These findings reveal that both BSCF and SSC can be stably operated for ORR under symmetric cell conditions; however, an appropriate current collection method is crucial to achieving stable performance.