Polarization-Induced Interface and Sr Segregation of in Situ Assembled La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ Electrodes on Y₂O₃–ZrO₂ Electrolyte of Solid Oxide Fuel Cells

Abstract

Application of cobaltite-based electrodes such as LaSrCoFeO (LSCF) on YO-ZrO (YSZ) electrolyte in solid oxide fuel cells (SOFCs) generally requires the use of a doped ceria barrier layer to prevent the interaction between LSCF and YSZ during sintering at high temperatures. In this paper, we report for the first time an in situ assembly approach to directly incorporate LSCF cathode to YSZ electrolyte without the use of a doped ceria barrier layer and without presintering at high temperatures. A Ni-YSZ anode-supported YSZ electrolyte cell with an in situ assembled LSCF electrode exhibits a peak power density of 1.72 W cm at 750 °C. However, the cell performance degrades significantly at 500 mAcm and 750 °C. The results indicate that cathodic polarization not only induces the formation of the interface but also accelerates the Sr segregation. The segregated Sr migrates to the LSCF electrode/YSZ electrolyte surface and forms an SrO layer. Using a Sr-free LaCoO composite cathode overcomes the Sr segregation problem, showing an excellent peak power density of 1.2 Wcm and good stability at 750 °C for over 100 h. The present study shows that cobaltite-based perovskites can be directly used on YSZ-based electrolyte via the in situ assembly providing an effective means to advance the application of highly active mixed ionic/electronic conducting cathodes to YSZ electrolyte-based SOFCs.

In Situ Formation of Er0.4Bi1.6O3 Protective Layer at Cobaltite Cathode/Y2O3–ZrO2 Electrolyte Interface under Solid Oxide Fuel Cell Operation Conditions

“…This implies the possible formation of SrZrO3 layer under the influence of cathodic polarization, similar to that observed for the directly assembled LSCF cathode on YSZ electrolyte. 63 The accumulation of Sr at the interface region implies the substantial Sr segregation and diffusion under cathodic polarization conditions, in good agreement with that reported in the literature. [65][66][67] for hetero-interfaces, in order to accommodate the lattice mismatch between two different phases.…”

“…H2 at a flow rate of 50 mL min -1 was supplied to the NiO-YSZ anode and the cathode was exposed to the ambient air. [60][61] However, in the case of LSCF-YSZ oxide couple, the reaction starts at a temperature as low as 800 o C. [62][63] This implies that the Nb The morphology of YSZ electrolyte surface in contact with directly assembled LSCFNb and ESB-LSCFNb cathodes is shown in Figure 3. The cathodes were either peeled off using adhesive tape (Figure 3b,d,f) or removed by acid treatment (Figure 3a,c,e).…”

A Multiscale Model for Electrochemical Reactions in LSCF Based Solid Oxide Cells

“…The bottom layer atoms were fixed at the bulk positions, the upper layer atoms were fixed at the bulk position along directions perpendicular to the slab, while the structure was fully relaxed. Due to the Sr segregation phenomenon at the interface which is commonly observed in the experiments, [50][51][52] the fifth atom layer, which is the interfacial layer between the two materials (shown in Fig. 3e), is chosen to be SrO layer.…”

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

“…Recently, we have shown the feasibility of applying directly assembled electrode on electrolyte without requiring further high temperature sintering, and the formation of electrode/electrolyte interface induced in situ by cathodic polarization [26][27][28][29][30][31][32][33][34][35]. In the case of LSM electrode and YSZ electrolyte, the initial results indicate that the electrochemical performance of cathodic polarization induced interface is comparable to that of the conventional pre-sintered electrodes, though the topography of the interface is very different, i.e.…”