Interfacial Stability between Air Electrode and Ceria‐Based Electrolyte under Cathodic Polarization in Solid Oxide Fuel Cells

Abstract

The stability of interfacial structure between air electrode and ceria‐based electrolyte (Sm2O3–CeO2, SDC) was evaluated under various polarization conditions at 1,000 °C. This is because the structural change at the interface is strongly related to the diffusion of constituent elements and has the potential to affect the long‐term stability. In this study, (La,Sr)MnO3 (LSM) and (La,Sr)(Co,Fe)O3 (LSCF) were applied as air electrodes. The cell with LSM/SDC interface showed the performance enhancement after cathodic polarization for 5 h, accompanied with the change in interfacial structure. The magnitude of the microstructural change as well as activation was dependent on the current density and the oxygen partial pressure. However, the active triple phase boundary (TPB)‐length decreased at every condition studied. On the other hand, no appreciable change in interfacial structure was confirmed for the LSCF/SDC system regardless of polarization conditions. In response to this phenomenon, the total TPB‐length was almost identical to the active one. The difference in morphological evolution at the interface depending on the electrode material was discussed.

Interface Solid-State Reactions in La0.8Sr0.2MnO3/Ce0.8Sm0.2O2 and La0.8Sr0.2MnO3/BaCe0.9Y0.1O3 Disclosed by X-ray Microspectroscopy

“…The chemical compatibility between electrolytes and electrode materials is one of the most discussed issues to overcome in order to improve SOFC stability and to increase the lifetime of the device. In particular, the study of solid-state reactivity between various SOFC components (interconnects, cermets, electrodes, and so forth) is a forefront topic in materials research. − Different approaches have been proposed to address such problems, for example, interposing layers that impede the interdiffusion of cations and therefore prevent the formation of secondary phases, , or alternatively, developing materials that are able to perform well at lower temperatures. In recent years, the materials chemistry research in the field has been oriented toward the development of intermediate temperature SOFC (IT-SOFC), operating at about 600–700 °C. , We recently investigated the compatibility between two important materials for IT-SOFC: the cathode La 0.6 Sr 0.4 Co 0.2 Fe 0.8 (LSCF) and the electrolyte Ce 0.8 Sm 0.2 O 2 (SDC) .…”

Interface formation and Mn segregation of directly assembled La0.8Sr0.2MnO3 cathode on Y2O3-ZrO2 and Gd2O3-CeO2 electrolytes of solid oxide fuel cells

“…The formation of an intimate electrode/electrolyte interface is thus critical in determining the performance and durability of SOFC cells, since it provides a direct pathway for oxygen species migration from electrode to electrolyte. In the case of LSM cathode, the formation of convex contact rings on YSZ and GDC electrolytes surface is observed after the high temperature pre-sintering [12,[16][17][18][19][20][21]. On the other hand, the significant effect of cathodic polarization on the electrode/electrolyte interface was observed under the fuel cell operation conditions, such as the formation of micro-pores and dense layer at the interface [18,[22][23][24], the increased TPB length [12], and the change of the electrolyte morphology [20,25].…”

“…In the case of LSM cathode, the formation of convex contact rings on YSZ and GDC electrolytes surface is observed after the high temperature pre-sintering [12,[16][17][18][19][20][21]. On the other hand, the significant effect of cathodic polarization on the electrode/electrolyte interface was observed under the fuel cell operation conditions, such as the formation of micro-pores and dense layer at the interface [18,[22][23][24], the increased TPB length [12], and the change of the electrolyte morphology [20,25]. Early studies show that polarization can broaden and flatten the edges of the contact rings and the significant topography change of the convex rings is most likely due to the incorporation of oxygen and/or the interdiffusion processes between LSM and YSZ electrolyte at the interface [17].…”

Interface Diffusion and Compatibility of (Ba,La)FeO3−δ Perovskite Electrodes in Contact with Barium Zirconate and Ceria

“…One of the key points for fabricating a performant SOFC or PCFC is the compatibility between cathode and electrolyte. , The relatively high operational temperature often leads to degradation of the materials involved, such as cation demixing, atomic species segregation, and secondary phases. − These processes can strongly influence cell performance, since insulating phases can form, decreasing the ionic and electronic conductivity across the cell. When cation interdiffusion leads to the formation of new phases (the classical example is La 2 Zr 2 O 7 in SOFC at the contact between LSM and YSZ), this is often detrimental as the new structure typically has inferior transport properties, and may also cause problems arising from volume changes or differences in thermal expansion.…”