Pressurized reversible solid oxide cell stack with integrated gas storage for CO2/CO processing

Fuel flexibility and reversibility are key advantages of solid oxide cells compared to low-temperature fuel cell technologies. However, operating with carbon-based feeds can introduce challenges, particularly when using nickel-based fuel electrodes, which exhibit high catalytic activity for carbon formation leading to electrode deactivation. This study evaluated a nickel-based 10-cell stack from Fraunhofer IKTS (Germany) for reversible operation with CO, CO 2 and O 2 as reactants. The stack was enclosed in a tight stainless-steel box enabling dead-end configuration on the oxygen side to target 100 % oxygen utilization during fuel cell operation. Pressurized electrolysis up to 5 bara enabled reuse of produced gas in subsequent reverse operation for potential in situ resource utilization of CO 2 for a Mars application. During electrolysis, the stack was operated at 820°C primarily with CO 2 with 4 % CO. Stable electrolysis operation achieved 74 % CO concentration at 5 bara, demonstrating that CO adequately sustains nickel electrode reduction and eliminates the need for external hydrogen co-feeding. The system underwent reversible SOC operation across two thermal cycles, with complete performance recovery. These results validate that conventional nickel-based SOCs can sustain Mars-relevant CO/CO 2 operation, but integrated gas purification, flushing systems or improved oxygen manifold sealing are required to enable practical deployment.