Microstructure tailoring of solid oxide electrolysis cell air electrode to boost performance and long-term durability

High-temperature solid oxide electrolysis cells (SOECs) offer higher efficiency compared to other electrochemical water splitting technologies and potentially could provide future technology to tackle the huge energy storage requirements created by the surge of intermittent solar and wind electricity availability. However, the lower electrochemical performance and long-term degradation of the SOEC electrodes are bottlenecks in the implementation of this technology. Herein, we report microstructure tailoring of a solid oxide cell air electrode via a simple method to significantly enhance the electrochemical performance and boost the air electrode stability. The air electrode microstructure was tailored by employing a graphite pore former and the cells were tested for SOEC performance and long-term durability under fuel cell (FC)-electrolysis cell (EC) cycles and a 1000 h chronopotentiometry test. The microstructural optimization resulted in a 30% increase in the SOEC performance for H2O conversion at 800 °C and significantly improved the long-term durability. Post-test SEM and TEM analyses indicated that, due to the microstructure tailoring, delamination of the air electrode was avoided and resistive interfaces forming Sr diffusion was suppressed within the barrier layer and electrolyte. Due to air electrode microstructure optimization, the buildup of the oxygen partial pressure across the electrolyte/barrier layer/air-electrode was reduced owing to increased triple phase boundary density, porosity at the interface, and larger active surface area of the electrode.