$\mathrm{Ba}(\mathrm{Ce},\mathrm{Zr})\mathrm{O}_3$-based electrodes for protonic ceramic electrochemical cells: towards highly compatible functionality and triple-conducting behavior

Protonic ceramic fuel cells (PCFCs) and electrolysis cells (PCECs) represent low- and intermediate-temperature electrochemical devices, which utilization allows chemical-to-electrical energy conversion with very high efficiency and low impact on the environment. To ensure long-term operability of PCFCs/PCECs as well as their up-scaling ability, a number of existing challenges, associated with chemical and thermal incompatibilities of the functional materials, should be overcome. This work aims at presenting a comprehensive overview of new electrodes materials based on barium cerate/zirconate, having structural fragments similar to that of the proton-conducting $\mathrm{Ba}(\mathrm{Ce},\mathrm{Zr})\mathrm{O}_3$ electrolytes and, correspondingly, high compatibility. Primary emphasis is paid to their functional properties such as chemical stability, thermal expansion behavior as well as transport features, which in turn determine electrochemical performance of the designed electrodes. In addition, possibility of tailoring triple-conducting materials is discussed as means of designing the electrodes with the highest electrochemical active surface area attractive for next-generation PCFCs/PCECs.