Solid–Solid Interfaces in Protonic Ceramic Devices: A Critical Review

Abstract

The literature concerning protonic ceramic devices is critically reviewed focusing the reader’s attention on the structure, composition, and phenomena taking place at solid–solid interfaces. These interfaces play a crucial role in the overall device performance, and the relevance of understanding the phenomena taking place at the interfaces for the further improvement of electrochemical protonic ceramic devices is therefore stressed. The grain boundaries and heterostructures in electrolytic membranes, the electrode–electrolyte contacts, and the interfaces within composite anode and cathode materials are all considered, with specific concern to advanced techniques of characterization and to computational modeling by ab initio approaches. An outlook about future developments and improvements highlights the necessity of a deeper insight into the advanced analysis of what happens at the solid–solid interfaces and of in situ/operando investigations that are presently sporadic in the literature on protonic ceramic devices.

Degradation issues and stabilization strategies of protonic ceramic electrolysis cells for steam electrolysis

“…Compared with oxygen ion-conducting SOECs, PCECs possess the distinct degradation mechanisms and behaviors, which deserve a comprehensive summary. Although there are several excellent comprehensive reviews on PCECs 5,8,9,[15][16][17][18][19][20] and topic reviews on the design of electrode materials for PCECs, [21][22][23][24][25] rare assessments focus on the degradation of PCECs for steam electrolysis. This has stimulated us to write this review on the degradation of PCECs, with emphasis on degradation mechanisms and mitigation strategies.…”

Solid-state compatibility of Ca:LaNbO4 with perovskite cathodes: Evidences from X-ray microspectroscopy

“…This study highlights the limited stability of lanthanum niobate against high-temperature treatments in contact with common perovskite cathodes, pointing out a severe issue in the long-term performance of SOFC devices based on these couples. Moreover, as previously put forward [8,12,19,20,31], Xray microprobe techniques are essential for assessing the solid-state compatibility in durable solid-state devices.…”

“…High proton conductivity is found in perovskites, especially barium cerates and zirconates, whose crystallochemical and electrochemical properties have been extensively investigated in the last decades. [4,5] Despite their appealing conductivity, those perovskites have either poor grain boundary conductivity (BaZrO3) or limited chemical stability to CO2 (BaCeO3): [6,7] even when the composition of cerates/zirconates is engineered to overcome the above issues, their chemical compatibility with the most common ceramic cathodes is less than ideal [8][9][10][11][12][13].…”

Enhanced Performance of Protonic Solid Oxide Steam Electrolysis Cell of Zr-Rich Side BaZr0.6Ce0.2Y0.2O3−δ Electrolyte with an Anode Functional Layer

“…The activation energy required for proton conductivity (∼0.5 eV) is also observed to be lower in SOECs using H + -conducting BaZr x Ce 1– x–y Y y O 3−δ (BZCY) perovskites relative to O-SOECs. 7 − 15 Similarly, the use of Zr-rich-phase BZCY perovskites in steam electrolysis applications is advantageous since the material becomes more tolerant to CO 2 and H 2 O as the Zr content increases. 16 , 17 However, cells using such a Zr-rich phase exhibits lower performance compared to cells using a Ce-rich phase.…”

“…However, the need for a high operating temperature leads to higher process costs and thermal degradation of materials. − Recent studies are now focused on protonic or H + ion-conducting SOEC (H-SOECs) because of its ability to operate at lower temperatures compared to O-SOECs. The activation energy required for proton conductivity (∼0.5 eV) is also observed to be lower in SOECs using H + -conducting BaZr x Ce 1– x–y Y y O 3−δ (BZCY) perovskites relative to O-SOECs. − Similarly, the use of Zr-rich-phase BZCY perovskites in steam electrolysis applications is advantageous since the material becomes more tolerant to CO 2 and H 2 O as the Zr content increases. , However, cells using such a Zr-rich phase exhibits lower performance compared to cells using a Ce-rich phase. This is due to the highly resistive nature of the grain boundary in the Y-doped BaZrO 3 moiety, which leads to substantial ohmic loss and interfacial polarization .…”