The Oxygen Reduction Kinetics of Mixed Conducting
                                                Electrodes: Model Considerations and Experiments on
                                                La0.6Sr0.4Co0.8Fe0.2O3 Microelectrodes

Fleig, Juergen; Baumann, F.; Maier, Joachim

doi:10.1149/200507.1636pv

Cited by 3 publications

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“…Here, j ano,TPB 0 (A m −1 ) is the exchange current density per unit length of the TPB and j cath,DPB 0 (A m −2 ) is the exchange current density per unit area of the DPB; ρ L TPB (m 3 m −1 ) is the TPB length density and ρ L DPB (m 3 m −2 ) is the DPB area density. The anodic and cathodic charge-transfer coefficients are taken from the porous Ni/YSZ anode measurements of de Boer [51] and from the LSCF cathode investigation of Fleig et al [52]. The activation overpotentials η act (V) are calculated as follows:…”

Section: Thermo-electric Modelmentioning

confidence: 99%

A Multiscale Approach to the Numerical Simulation of the Solid Oxide Fuel Cell

et al. 2019

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The models of solid oxide fuel cells (SOFCs), which are available in the open literature,may be categorized into two non-overlapping groups: microscale or macroscale. Recent progressin computational power makes it possible to formulate a model which combines both approaches,the so-called multiscale model. The novelty of this modeling approach lies in the combination ofthe microscale description of the transport phenomena and electrochemical reactions’ with thecomputational fluid dynamics model of the heat and mass transfer in an SOFC. In this work,the mathematical model of a solid oxide fuel cell which takes into account the averaged microstructureparameters of electrodes is developed and tested. To gain experimental data, which are used toconfirm the proposed model, the electrochemical tests and the direct observation of the microstructurewith the use of the focused ion beam combined with the scanning electron microscope technique(FIB-SEM) were conducted. The numerical results are compared with the experimental data fromthe short stack examination and a fair agreement is found, which shows that the proposed modelcan predict the cell behavior accurately. The mechanism of the power generation inside the SOFC isdiscussed and it is found that the current is produced primarily near the electrolyte–electrode interface.Simulations with an artificially changed microstructure does not lead to the correct prediction of thecell characteristics, which indicates that the microstructure is a crucial factor in the solid oxide fuelcell modeling.

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Section: Thermo-electric Modelmentioning

confidence: 99%

A Multiscale Approach to the Numerical Simulation of the Solid Oxide Fuel Cell

et al. 2019

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“…In the case of a tubular geometry, a large number of mesh elements are generally necessary because of the large ratio between the length and thickness of the layers, which is of the order of 500‐1,000 (Hwang et al , 2005; Fleig et al , 2005). A second particular feature of such a geometrical configuration concerns the non negligible effects of radiation heat transfer in both the single cells (Haynes and Wepfer, 2001) and in the stacks (Verda and Borchiellini, 2007).…”

Section: Introductionmentioning

confidence: 99%

Entropy generation analysis for the design optimization of solid oxide fuel cells

Sciacovelli

Verda

2011

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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PurposeThe aim of this paper is to investigate performance improvements of a monolithic solid oxide fuel cell geometry through an entropy generation analysis.Design/methodology/approachThe analysis of entropy generation rates makes it possible to identify the phenomena that cause the main irreversibilities in the fuel cell, to understand their causes and to propose changes in the design and operation of the system. The various contributions to entropy generation are analyzed separately in order to identify which geometrical parameters should be considered as the independent variables in the optimization procedure. The local entropy generation rates are obtained through 3D numerical calculations, which account for the heat, mass, momentum, species and current transport. The system is then optimized in order to minimize the overall entropy generation and increase efficiency.FindingsIn the optimized geometry, the power density is increased by about 10 per cent compared to typical designs. In addition, a 20 per cent reduction in the fuel cell volume can be achieved with less than a 1 per cent reduction in the power density with respect to the optimal design.Research limitations/implicationsThe physical model is based on a simple composition of the reactants, which also implies that no chemical reactions (water gas shift, methane steam reforming, etc.) take place in the fuel cell. Nevertheless, the entire procedure could be applied in the case of different gas compositions.Practical implicationsEntropy generation analysis allows one to identify the geometrical parameters that are expected to play important roles in the optimization process and thus to reduce the free independent variables that have to be considered. This information may also be used for design improvement purposes.Originality/valueIn this paper, entropy generation analysis is used for a multi‐physics problem that involves various irreversible terms, with the double use of this physical quantity: as a guide to select the most relevant design geometrical quantities to be modified and as objective function to be minimized in the optimization process.

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Numerical Simulation of SOFC Electrode Polarization Using Three-Dimensional Microstructure Reconstructed by FIB-SEM

Shikazono

Kasagi

2012

MRS Proc.

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Three-dimensional numerical simulations can provide information which cannot be obtained from experiments and can be a powerful tool for investigating reaction phenomena in solid oxide fuel cell (SOFC) electrodes. In the present study, a dual-beam focused ion beamscanning electron microscope is used to reconstruct the three dimensional microstructures of the SOFC electrodes, and their polarization characteristics are predicted by a lattice Boltzmann method. Predicted overpotentials for Ni-YSZ anode and mixed ionic and electronic conducting cathode (La0.6Sr0.4Co0.2Fe0.8O3-δ; LSCF6428) are compared with the experimental data for validation. In addition, three-dimensional distributions of electrochemical potential and current densities inside the electrode microstructures are obtained. Large non-uniformities of potential and current distributions are found in the Ni-YSZ anode, while those became much uniform in the LSCF cathode. The present method can be expected as a powerful tool for investigating local potential fields which affect local reactions and diffusion processes as well as local physical properties of the SOFC electrodes.

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The Oxygen Reduction Kinetics of Mixed Conducting Electrodes: Model Considerations and Experiments on La0.6Sr0.4Co0.8Fe0.2O3 Microelectrodes

Cited by 3 publications

References 0 publications

A Multiscale Approach to the Numerical Simulation of the Solid Oxide Fuel Cell

A Multiscale Approach to the Numerical Simulation of the Solid Oxide Fuel Cell

Entropy generation analysis for the design optimization of solid oxide fuel cells

Numerical Simulation of SOFC Electrode Polarization Using Three-Dimensional Microstructure Reconstructed by FIB-SEM

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