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This paper describes the development and testing of a 1 kW reversible solid oxide fuel cell intended for energy storage on space exploration missions, particularly for long term Mars exploration. The energy is stored as H2 or CO produced by electrolysis of H2 O or CO2 . The reactants are then converted back to its original composition by producing electricity.The breadboard was operated for 1250 hours alternating between electrolyser mode and fuel cell mode with H2 /H2 O as reactants. During the tests, as long as the mechanical integrity of the system was maintained, no degradation effect was observed. At the end of the test period, the fuel cell was operated for three full cycles (approx. 50 hours) with CO/CO2 as reactants. The performance on CO/CO2 was lower than for hydrogen, but sufficient to be used in a compact energy storage system for Mars exploration.

A challenging barrier for the broad, successful implementation of Reversible Solid Oxide Fuel Cell (RSOFC) technology for Mars application utilizing CO2 from the Martian atmosphere as primary reactant, remains the long term stability by the effective control and minimization of degradation resulting from carbon built up. The perovskitic type oxide material La0.75 Sr0.25 Cr0.9 Fe0.1 O3-δ (LSCF) has been developed and studied for its performance and tolerance to carbon deposition, employed as bi-functional fuel electrode in a Reversible SOFC operating on the CO2 cycle (Solid Oxide Electrolysis Cell/SOEC: CO2 electrolysis, Solid Oxide Fuel Cell/SOFC: power generation through the electrochemical reaction of CO and oxygen). A commercial state-of-the-art NiO-YSZ (8% mol Y2 O3 stabilized ZrO2 ) cermet was used as reference material. CO2 electrolysis and fuel cell operation in 70% CO/CO2 were studied in the temperature range of 900-1000°C. YSZ was used as electrolyte while LSM-YSZ/LSM (La0.2 Sr0.8 MnO3 ) as oxygen electrode. Results showed that LSCF had high and stable performance under RSOFC operation.