Highly active and CO₂-tolerant Sr₂Fe_1.3Ga_0.2Mo_0.5O_6-δ cathode for intermediate-temperature solid oxide fuel cells

The development of cathode materials, with high catalytic activity toward oxygen reduction reaction (ORR), structural stability and CO₂ tolerance, is an important research direction for the successful realization of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, a novel double perovskite mixed ionic conductor, i.e., Sr₂Fe_1.3Ga_0.2Mo_0.5O_6-δ (SFGM), is developed by Ga-doping at Fe-sites of Sr₂Fe_1.5Mo_0.5O_6-δ (SFM) and evaluated as a cathode material in IT-SOFCs. At 750 °C, the area specific resistance (ASR) of SFGM cathode is found to be 0.099 Ω cm², which is ~50% lower than SFM cathode (0.224 Ω cm²) in 20% O₂/N₂ atmosphere. Moreover, SFGM exhibits outstanding CO₂ tolerance due to its excellent CO₂ adsorption resistance compared with SFM. The ASR of SFGM remains stable at ~0.13 Ω cm² during 100 h of continuous operation in 5% CO₂-containing air. In addition, a large-sized SFGM cathode (30 cm²) is utilized in anode-supported flat-tube SOFCs to demonstrate the potential of SFGM in practical applications. At 750 °C, the as-prepared SFGM-based single-cell provides a stable power of 12 W for 291 h in 5% CO₂-containing air. The superior electrochemical performance and outstanding CO₂ tolerance of SFGM are promising features for the rapid development of IT-SOFCs.