Progress and potential for symmetrical solid oxide electrolysis cells

Recently, symmetrical solid oxide electrolysis cells (SSOECs) with the same electrode materials as both the anode and cathode have attracted lots of attention because of their simple manufacturing process and low cost. Moreover, this can narrow the trouble of chemical incompatibility and thermal mismatching, and also, these SSOECs are more convenient in practical applications without the distinction of the cathode and anode. However, there is no comprehensive and critical review to summarize the recent progress of SSOECs so far. In this paper, their development history, fundamental mechanisms, electrolyte and electrode materials, and fabrication methods are highlighted. Fuel-assisted SSOECs that decrease overpotential and other applications based on SSOECs are introduced. Furthermore, the challenges and prospects for future research into SSOECs are included, to some extent offering critical insights and useful guidelines for the knowledge-based rational design of better electrodes for commercially viable SSOECs.