Review—Materials Degradation of Solid Oxide Electrolysis Cells

Renewable energy sources such as solar and wind power are important for the future energy supply chain, but require suitable energy storage and conversion technologies due to the nature of the intermittency in electricity generation. Solid oxide cell (SOC) is such a highly efficient device which can store the renewable electricity into chemical energy of fuels under solid oxide electrolysis cell (SOEC) operation mode and to regenerate the electricity using the stored fuels under solid oxide fuel cell (SOFC) operation mode. However, there are significant technological barriers for the commercial viability of SOCs, one of them is the significant performance degradation under the SOEC mode. This paper reviews critically the durability and performance degradation issues of SOCs under SOEC operation conditions and the emphasis is mainly on the physical, chemical and microstructural processes that cause the degradation and their dependence on the operation conditions and nature of the oxygen and hydrogen electrodes and electrolyte materials. The degradation due to the contaminants such as chromium, boron and silica from metallic interconnect, borosilicate glass sealants and/or raw materials is also reviewed. The development of high performance and durable SOECs technology is discussed and based on the observed evidences, the sequence of the delamination processes at the oxygen electrode/YSZ electrolyte has been proposed.