Electrolyte-electrode interface: A key factor for advanced protonic ceramic electrochemical cells

Protonic ceramic fuel/electrolysis cells (PCFCs/PCECs) show great potential for the efficient and reversible conversion of chemical and electrical energy. The electrolyte and oxygen electrode interface in PCFCs/PCECs is particularly crucial for achieving optimal performance. In this work, Ba evaporation and Y enrichment phenomena are investigated on the surface of a BaCe0.7Zr0.1Y0.2O3-δ electrolyte during high-temperature sintering. Furthermore, an interfacial engineering strategy is proposed by removing the non-stoichiometric perovskite surface layer via a facile polishing process to enable a comparative analysis of the detrimental effects of the undesired layer on the cell performance. Polishing the electrolyte leads to a remarkable ∼50 % enhancement in PCFC performance and ∼120 % enhancement in PCEC performance at 650 °C. Electrochemical impedance spectroscopy coupled with distribution of relaxation time analysis reveals that the improved performance of the polished cell can be attributed to reductions in both the ohmic and polarization losses, with the latter primarily influenced by the facilitated oxygen electrode reactions. This interfacial engineering approach restores the high proton conductivity at the electrolyte surface and strengthens the physical and chemical adhesion between the electrolyte and the oxygen electrode. Our findings shed light on the existing challenges at the electrolyte-electrode interface and underscore the significance of interfacial engineering in enhancing PCFC/PCEC performance.