Understanding the electrochemical behaviour of LSM-based SOFC cathodes. Part II - Mechanistic modelling and physically-based interpretation

Abstract

This study presents a physically-based model for the impedance simulation of the oxygen reduction reaction in porous strontium-doped lanthanum manganite (LSM) cathodes. The model describes the surface mechanism only, taking into account the co-limited adsorption/diffusion of oxygen and the charge-transfer reaction at the three-phase boundary (TPB). After calibration with experimental impedance spectra, the model is used to identify the transition of kinetic regime from the surface to the bulk path mechanism, which occurs at cathodic dc bias of ca. 0.2. V within 700-800. C. The transition is highlighted by a significant decrease in impedance and the appearance of a low-frequency inductive loop. The model consistently reproduces the impedance spectra before the transition of kinetic regime with a single set of parameters, allowing for the deconvolution of two features, one associated with the co-limited adsorption/diffusion process (ca. 5. Hz) and another minor contribution due to the charge-transfer at the TPB (ca. 35. Hz). The model and its parameters, which quantitatively agree with the literature, can be used as a basis to optimize the microstructural and surface properties of technical LSM-based cathodes, showing that the TPB length is not the main parameter to be maximized

Infiltration, Overpotential and Ageing Effects on Cathodes for Solid Oxide Fuel Cells: La0.6Sr0.4Co0.2Fe0.8O3-δversus Ba0.5Sr0.5Co0.8Fe0.2O3-δ

“…40 Moreover, LSM possess: (i) good electrochemical activity toward the Oxygen Reduction Reaction (ORR) and high electronic conductivity, [50][51][52] (ii) excellent stability, 53,54 (iii) increased activity under a cathodic overpotential. 40,[55][56][57][58][59] The effect of LSMimpregnation, on the degradation of LSCF and BSCF porous cathodes, was studied through impedance spectroscopy, XRD and SEM-EDX investigations. Furthermore, an analysis of C chem as a function of DC overpotential was performed, in order to acquire information on the capability of the two materials of storing oxygen vacancies under an applied DC overpotential.…”

Tri‐Functional Double Perovskite Oxide Catalysts for Fuel Cells and Electrolyzers

“…In transition case, a theoretical simulation by Bertei et al. suggests that, as DC bias increases, surface diffusion cannot supply enough adsorbed oxygen to the TPB and the bulk diffusion path is activated [56] . Thus, in the present case, above 0.2 V, the bulk migration of oxygen ions could be the dominant process.…”

“…The shift in the peak position of P3 could be related to the transition between two regimes of surface process, that is, from the surface diffusion of oxygen atoms to the bulk diffusion of oxygen ions [56] . Elsewhere, a similar transition in cathodic process was observed in La 1‐ x Sr x MnO 3‐ δ (LSM) exactly at 0.2 V of applied DC bias [56] . In the case of LSM, the surface path is favored at lower bias and the bulk path is preferred at higher bias.…”

A review of solid oxide fuel cell component fabrication methods toward lowering temperature

“…A cathode is occupied on another side of the anode which sandwiches with electrolyte in the middle part. 29,46 To avoid the degradation cell, the compatibility of each component and external thermo-mechanical stress is important to matched each other to give positive condition to the SOFC performance. Usually, the degradation of cathode electrolyte performance is caused by poisoning and corrosion issues from the contamination of external factor such as the oxidant came from air surrounding which contained the pollutions.…”

“…45 The advantages of LSMbased electrode are the high conductivity property until 100 S cm -1 at the 600°C and the coefficient of thermal expansion well matched with YSZ electrolyte (12.5 × 10 -6 K -1 ). 29,46 To avoid the degradation cell, the compatibility of each component and external thermo-mechanical stress is important to matched each other to give positive condition to the SOFC performance. 47 Therefore, the bilayer electrode and electrolyte is designed to facilitate the ion or proton diffusion to complete the cells such as the formation of YSZ electrolyte with LSM based cathode which useful to reduce the operating temperature of SOFC application.…”