Recent advances in high temperature solid oxide electrolytic cells

Solid oxide electrolytic cells (SOECs) with oxygen ion or proton conducting electrolyte have received extensive attention in recent years as a kind of energy storage technology. SOECs achieve the synthesis of chemicals such as hydrogen, CO or syngas by electrolyzing water, CO₂ or both at high temperature. This review presents the basic structure and electrochemical principle of SOECs, then introduces the recent research progress of cathodes, anodes and electrolytes in SOECs, and particularly points out the current challenges of SOEC materials, such as inactivation at high temperatures and decay due to long-term operation. We summarize various strategies to improve the properties of different electrode materials, including doping, in situ exsolution and microstructure modification. Moreover, the advantages and disadvantages of different SOEC stack structures (planar and tubular) are also outlined. The commercialization of SOECs in different countries is also presented. Finally, the future development trends in novel materials and engineering design of SOECs are proposed.