Solid Oxide Fuel Cell Cathodes: Importance of Chemical Composition and Morphology

Abstract

The main aspects of the cathode materials morphology for Intermediate Temperature Solid Oxide Fuel Cells (IT SOFC) are considered in this paper. The approaches for estimation of their basic properties, e.g. oxygen mobility and surface reactivity, are described and the results of different techniques (e.g. weight and conductivity relaxation, oxygen isotope exchange) application for studies of powders and dense ceramic materials are compared. The Ruddlesden-Popper type phases (e.g. Pr2NiO4) provide enhanced oxygen mobility due to cooperative mechanism of oxygen interstitial migration. For perovskites, the oxygen mobility is increased by doping, which generates oxygen vacancies or decreases metal-oxygen bond strength. Nonadditive increasing of the oxygen diffusion coefficients found that for perovskite-fluorite nanocomposites, it can be explained by the fast oxygen migration along perovskitefluorite interfaces. Functionally graded nanocomposite cathodes provide the highest power density, the lowest area specific polarization resistance, and the best stability to degradation caused by the surface layer carbonization/ hydroxylation, thus being the most promising for thin film IT SOFC design.

A Novel Approach for Fabricating LaMnO3 Thin Films Using Combined Microwave Combustion and Pulsed Electron Deposition Techniques

“…In particular, solid oxide fuel cells (SOFCs) have been extensively studied and attracted much attention as a promising way to generate electricity at high efficiency and low cost [18][19][20]. For such applications, the cathode material must satisfy several criteria such as good electrical conductivity, high porosity to allow gas diffusion, thermal expansion coefficient matching well with that of the solid electrolyte, and chemical stability at a high temperature [21][22][23]. Most of the requirements listed above are satisfied by LaMnO 3 perovskites, making it one of the most suitable materials for cathode in SOFCs [24].…”

Advancements in Perovskite‐Based Cathode Materials for Solid Oxide Fuel Cells: A Comprehensive Review

“…Therefore, different studies revealed different values for oxygen flux using different approaches for LSCF production with a stoichiometric ratio composition. [119,120] For instance, four methods, namely, coprecipitation (CP), solid-state reaction (SS), spray-pyrolysis (SP), and citrate acetate (CA) were used to synthesize La 0.8 Sr 0.2 Co 0.6 Fe 0.4 O 3 membranes with the aim to investigate the effect of these methods on the microstructure and composition, and ultimately the electrical conductivity of the membranes. The observed density for all the membranes were found to be 97 % of the theoretical value.…”

Design of Mixed Ionic-Electronic Materials for Permselective Membranes and Solid Oxide Fuel Cells Based on Their Oxygen and Hydrogen Mobility

“…The Ruddlesden–Popper (RP) phases with the general formula of (AO)(ABO 3 ) n or A n+1 B n O 3n+1 consist of the perovskite layers ABO 3−δ alternating with the rock salt layers A 2 O 2+δ [ 58 , 60 , 63 , 69 , 129 , 159 , 285 , 286 , 287 , 288 , 289 , 290 ]. The important feature of RP phases, which makes them attractive SOFC cathodes and oxygen-separation-membrane materials, is a fine oxygen transport provided via the cooperative mechanism of oxygen migration.…”

“…The important feature of RP phases, which makes them attractive SOFC cathodes and oxygen-separation-membrane materials, is a fine oxygen transport provided via the cooperative mechanism of oxygen migration. In this case, both lattice and interstitial oxide anions accumulating at a high level are involved in the process of oxygen transport ( Figure 20 ) [ 55 , 58 , 60 , 63 , 69 , 159 , 285 , 288 , 291 , 292 , 293 , 294 , 295 , 296 , 297 ]. This allows them to reach superior oxygen mobility compared to other MIECs ( Figure 21 ).…”

“…In contrast to cathodes made of materials with dominant electronic conductivity, whose performance is limited by the triple-phase boundary (TPB), the performance of MIEC cathodes is limited by the double-phase boundary (DPB). It stimulates the oxygen reduction reaction at the cathode and enhances ion transport to the electrolyte [ 58 , 60 , 61 , 62 ].…”