CO₂ electroreduction reaction (CO₂RR), combined with solid oxide electrolysis cells (SOECs), is a feasible technology for the storage of renewable electric energy, while its development is limited by the catalytic activity and stability on cathodes. Here, a novel garnet oxide (Gd₃Fe₅O₁₂) cathode is designed, where the garnet oxide is converted to perovskite oxide and iron via in situ electrochemical phase transition during CO₂ electroreduction, resulting in high activity with Faradaic efficiency close to 100% and great stability over 1000 h galvanostatic test. A variety of experimental characterizations and density functional theory calculations indicate that in situ exsolved Fe clusters can effectively enhance the adsorption energies of intermediates and lowering the CO₂ dissociation barriers. Microkinetic modelling confirms that CO₂RR goes through a dissociative adsorption mechanism and the electronic transfer for CO₂ dissociation is the rate-determining step.

CO ₂电还原反应（CO ₂ RR）结合固体氧化物电解槽（SOECs）是一种可行的可再生电能存储技术，但其发展受到阴极催化活性和稳定性的限制。在这里，设计了一种新型石榴石氧化物 (Gd ₃ Fe ₅ O ₁₂ ) 阴极，其中石榴石氧化物通过CO ₂期间的原位电化学相变转化为钙钛矿氧化物和铁电还原，导致法拉第效率接近 100% 的高活性和超过 1000 小时恒电流测试的稳定性。各种实验表征和密度泛函理论计算表明，原位溶出的Fe团簇可以有效提高中间体的吸附能并降低CO ₂解离势垒。微动力学模型证实 CO ₂ RR 经历解离吸附机制，CO ₂解离的电子转移是速率决定步骤。