Reversible solid oxide cell for CO/CO2-based fuels with perovskite-based fuel electrode

• Reversible operation in CO/CO 2 with perovskite-type fuel electrode of button cells and short-stack. • Analysis of EIS and DRT based on various testing conditions. • Stable cell voltage with minimal degradation over 1400 h of electrolysis without signs of carbon formation. Solid oxide cells (SOCs) are a highly efficient technology capable of converting carbon dioxide (CO 2 ) into carbon monoxide (CO) and oxygen (O 2 ) and vice versa. Nickel oxide (NiO) is the most widely used fuel electrode material due to its reduction to metallic nickel in a fuel atmosphere, which imparts high electronic conductivity and catalytic activity. When combined with an electrolyte material to form a cermet electrode, it gains high ionic conductivity. This work evaluates and compares several electrode materials, including perovskites and state-of-the-art nickel cermet, and focuses on alternatives that address a critical limitation of carbon-based fuels: carbon deposition. A solid oxide cell incorporating an alternative material, (PrBa) 0.95 Fe 1.8 Mo 0.2 O 5 mixed with Ce 0.8 Gd 0.2 O 2 , was tested in both electrolysis and fuel cell modes. Lower area specific resistance (ASR) was achieved compared to nickel cermet (cer- ceramic, met- metal) button cell when appropriate current collector was applied. The role of gas composition, specifically CO/CO 2 , was investigated using electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT). Through DRT analysis, CO adsorption and charge transfer at the fuel electrode were identified as the primary contributor to overall resistance. Moreover, stable performance over 1400 h was achieved in CO 2 -rich electrolysis environment. Additionally, a short-stack comprising five cells was assembled and tested under a CO/CO 2 fuel atmosphere, achieving carbon-free operation. However, to achieve performance comparable to button cell, further stack design modifications must be implemented before further scale-up. These results highlight the potential of alternative materials as substitutes for nickel-based fuel electrodes, particularly for carbon-based fuels. This study contributes to the development of sustainable energy systems, with implications for future manned missions to Mars.