Electrochemistry and energy conversion features of protonic ceramic cells with mixed ionic-electronic electrolytes

Protonic ceramic electrochemical cells (including fuel cells (PCFCs) and electrolysis cells (PCECs)) are positioned as an eco-friendly means for realizing energy/chemical conversion at low (below 500 °C) and intermediate (500–800 °C) temperatures; as a result, R&D of PCFCs and PCECs are compatible with hydrogen energy and CO2 utilization programs that play an increasing role in global environmental practice. However, along with ionic transport, the majority of proton-conducting ceramic materials also exhibit electronic transport under oxidizing conditions and elevated temperatures. This feature negatively affects the performance of cells due to the short-circuit effect leading to a reduction in faradaic and energy efficiencies. In response, in order to achieve a compromise between high performance and high efficiency, the present review article aims at revealing the main factors contributing to undesirable electronic transport of materials used in PCFCs and PCECs, as well as possible solutions leading to its suppression for improving their efficiency.