Effective Transport Coefficients for Porous Microstructures in Solid Oxide Fuel Cells

Choi, Haechul; Berson, Arganthaël; Kenney, Ben; Pharoah, Jon G.; Beale, Steven; Karan, Kunal

doi:10.1149/1.3205663

Cited by 14 publications

(17 citation statements)

References 29 publications

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“…17, is the porosity and is the tortuosity. The electrode tortuosity has been estimated 37,38 to be 2. The Knudsen diffusivity, which depends on the average pore diameter, D K eff , is…”

Section: ͓16͔mentioning

confidence: 99%

Estimation of Chemical and Transport Processes in Porous, Stoichiometric LSM Cathodes Using Steady-State Polarization and Impedance Modeling

Kenney

Karan

2010

J. Electrochem. Soc.

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Electrochemical data collected for the porous La1−xSrxMnO3±δ (LSM) cathode–yttria-stabilized zirconia electrolyte system were analyzed using a mathematical model capable of simulating both the steady-state and impedance responses. The model considered the distributed nature of the porous electrode and a parallel pathway for oxygen transport including gas transport and surface diffusion. Data were collected in low oxygen partial pressures ranging between 10−4 and 10−3atm , where LSM was considered to be stoichiometric with respect to oxygen. Thermodynamically consistent kinetic and transport parameters were regressed from the steady-state polarization data. Three different parameter sets fit the general trend of the experimental data. The surface diffusion and adsorption/desorption parameters were cross-correlated, which underlines the difficulty in finding a unique set of fitting parameters. The parameter set with four adjustable parameters resulted in a high surface diffusion coefficient but slower adsorption/desorption kinetics compared to the other two parameter sets for which a lower surface diffusion coefficient was fixed. The predicted overall impedance at zero-dc bias conditions for three parameter sets had varying degrees of agreement with the data. Low and high frequency arcs attributed to adsorption and an oxygen transport process were observed in the faradaic impedance response.

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“…17, is the porosity and is the tortuosity. The electrode tortuosity has been estimated 37,38 to be 2. The Knudsen diffusivity, which depends on the average pore diameter, D K eff , is…”

Section: ͓16͔mentioning

confidence: 99%

Estimation of Chemical and Transport Processes in Porous, Stoichiometric LSM Cathodes Using Steady-State Polarization and Impedance Modeling

Kenney

Karan

2010

J. Electrochem. Soc.

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“…One method of gaining insight into these relationships is the development of detailed three-dimensional ͑3D͒ electrode geometry models, either numerically [1][2][3][4][5][6] or by constructing representations of real electrodes using methods such as focused ion beam-scanning electron microscopy ͑FIB-SEM͒ [7][8][9][10] or X-ray computed tomography ͑XCT͒. 11,12 Key microstructural parameters such as the connected three-phase boundary length ͑TPBL͒ density 1,4 and effective transport properties such as electronic and ionic conductivities and gas diffusivity 13 can be extracted from the resulting geometrical models. These volume averaged properties can then be used in continuum electrode models for electrochemical performance evaluation.…”

mentioning

confidence: 99%

Connected Three-Phase Boundary Length Evaluation in Modeled Sintered Composite Solid Oxide Fuel Cell Electrodes

Metcalfe

Kesler

Rivard

et al. 2010

J. Electrochem. Soc.

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A numerical methodology for evaluating the three-phase boundary length ͑TPBL͒ in sintered composite solid oxide fuel cell electrodes is developed. Three-dimensional models of a representative volume element of sintered composite electrodes are generated for which the mean particle diameter, composition, and total porosity may be specified as input parameters. Tomographic methods are used to reconstruct the modeled electrode and the percolation for each phase is evaluated. The connected TPBL is calculated for a range of electrode designs and comparisons are made with calculated TPBL values available in the literature. The maximum connected TPBL occurred at a porosity of 0.21 and at equal solid volume fractions of ionic and electronic conducting phases for particles having the same mean diameter and particle size variance. A cubic envelope having a minimum length of 14 times the mean particle diameter was necessary to adequately represent the electrode structure.Design and fabrication of solid oxide fuel cell ͑SOFC͒ electrodes require careful attention to the relationships between electrode performance and both material composition and microstructure. One method of gaining insight into these relationships is the development of detailed three-dimensional ͑3D͒ electrode geometry models, either numerically 1-6 or by constructing representations of real electrodes using methods such as focused ion beam-scanning electron microscopy ͑FIB-SEM͒ 7-10 or X-ray computed tomography ͑XCT͒. 11,12 Key microstructural parameters such as the connected three-phase boundary length ͑TPBL͒ density 1,4 and effective transport properties such as electronic and ionic conductivities and gas diffusivity 13 can be extracted from the resulting geometrical models. These volume averaged properties can then be used in continuum electrode models for electrochemical performance evaluation. For example, Wilson et al. 14 modified the Tanner-Fung-Virkar model 15 to include phase connectivity and tortuosity obtained from reconstruction of La 0.8 Sr 0.2 MnO 3 -Y 2 O 3 -stabilized ZrO 2 ͑YSZ͒ cathodes, improving the agreement between measured and calculated polarization resistance. The development of electrode performance models that make direct use of 3D microstructural models 3,9,11,16 rather than volume averaged properties may provide further insight into the relationships between electrode performance and material composition and microstructure at the cost of increased computation time.Numerical generation of electrode microstructure models and the digital reconstruction of electrodes each have advantages and disadvantages pertaining to the elucidation of electrode structureperformance relationships. Numerical generation of electrode structures allows comparatively rapid evaluation of a wide range of electrode parameters. The resulting structures are deterministic in the sense that microstructural parameters such as the total TPBL can be determined analytically. However, the connectivity of the pore space is difficult to evaluate due to the presence...

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“…Regarding SOFCs, Choi et al (2009) analyzed the effective electrical and ionic conductivity and gas diffusivity (including Knudsen diffusion) of the anode and cathode electrodes. The microstructures were made of randomly distributed and overlapping spheres with particle size distributions that matched those of ceramic powders.…”

Section: U N C O R R E C T E D P R O O Fmentioning

confidence: 99%

“…The microstructure of the porous media can be obtained from (1) tomography images (García-Salaberri et al 2015a, b, 2018 or can be (2) virtually generated using numerical algorithms (Choi et al 2009;Choi et al 2011;Bertei et al 2014). Volumeaveraged quantities (e.g., composition fraction) and statistical descriptors (e.g., pore size distribution, n-point correlation functions, lineal path function, and chord length function) can be used as objective variables (Pant et al 2014).…”

Section: Geometrymentioning

confidence: 99%

Effective Transport Properties

García-Salaberri

2022

Electrochemical Cell Calculations With OpenFOAM

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Porous media are an integral part of electrochemical energy conversion and storage devices, including fuel cells, electrolyzers, redox flow batteries and lithium-ion batteries, among others. The calculation of effective transport properties is required for designing more efficient components and for closing the formulation of macroscopic continuum models at the cell/stack level. In this chapter, OpenFOAM is used to determine the effective transport properties of virtually-generated fibrous gas diffusion layers. The analysis focuses on effective properties that rely on the fluid phase, diffusivity and permeability, which are determined by solving Laplace and Navier-Stokes equations at the pore scale, respectively. The model implementation (geometry generation, meshing, solver settings and postprocessing) is described, accompanied by a discussion of the main results. The dependence of orthotropic effective transport properties on porosity is examined and compared to traditional correlations presented in the literature.

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Effective Transport Coefficients for Porous Microstructures in Solid Oxide Fuel Cells

Cited by 14 publications

References 29 publications

Estimation of Chemical and Transport Processes in Porous, Stoichiometric LSM Cathodes Using Steady-State Polarization and Impedance Modeling

Estimation of Chemical and Transport Processes in Porous, Stoichiometric LSM Cathodes Using Steady-State Polarization and Impedance Modeling

Connected Three-Phase Boundary Length Evaluation in Modeled Sintered Composite Solid Oxide Fuel Cell Electrodes

Effective Transport Properties

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