Simulation of a composite cathode in solid oxide fuel cells

Chen, X.J.; Chan, Siew Hwa; Khor, K.A.

doi:10.1016/j.electacta.2003.12.015

Cited by 162 publications

(113 citation statements)

References 27 publications

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“…Therefore, a high electrode porosity is desired to improve the electric performance of an SOEC for CO 2 electrolysis. However, it should be mentioned that the activation overpotentials are assumed to be independent of the electrode microstructures, which is valid for conventional SOEC electrodes and might be invalid for advanced composite electrodes [24,25]. In order to account for the electrode structural effect on activation overpotentials, micro-scale modeling is needed.…”

Section: Operating and Structural Parameters On Soec Performancementioning

confidence: 99%

Modeling of a solid oxide electrolysis cell for carbon dioxide electrolysis

2010

Chemical Engineering Journal

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In this study, 2 models are developed to investigate the performance of a solid oxide electrolysis cell (SOEC) for CO 2 electrolysis at different levels. The first model is a one-dimensional model which is basing on a previously developed electrochemical model for steam electrolysis and considered all overpotentials in the SOEC. The second model is a two-dimensional thermal-fluid model consisting of the 1D model and a computational fluid dynamics (CFD) model. It is found that the mean electrolyte temperature initially decreases with increasing operating potential, reaches the minimum at about 1.1V and increases considerably with a further increase in potential. At the thermal-neutral voltage (1.463V at 1173K), the calculated mean electrolyte temperature matches the inlet gas temperature. Increasing the operating potential increases both the local current density and the electrolyte Nernst potential. The electrochemical performance can be improved by increasing the inlet gas velocity from 0.2ms -1 to 1.0ms -1 but further increasing the inlet gas velocity will not considerably enhance the SOEC performance. It is also found that a change of electrode permeability in the order of 10 -16 -10 -13 m 2 does not noticeably influence the SOEC performance in the present study, due to negligible convection effect in the porous electrodes.

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Section: Operating and Structural Parameters On Soec Performancementioning

confidence: 99%

Modeling of a solid oxide electrolysis cell for carbon dioxide electrolysis

2010

Chemical Engineering Journal

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“…[8][9][10][11][12][13][14][15][16] These models may include the gas-phase species transport through the pore phase, surface diffusion of adsorbed species, Ohm's law for the charge transport within the ionic and electronic conducting phases, charge balance, and charge-transfer kinetics. The models are formulated in a continuum differential-equation setting, and usually in one spatial dimension through the electrode thickness.…”

Section: ͓3͔mentioning

confidence: 99%

Modeling Elementary Heterogeneous Chemistry and Electrochemistry in Solid-Oxide Fuel Cells

Zhu

Kee

Janardhanan

et al. 2005

J. Electrochem. Soc.

504

523

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This paper presents a new computational framework for modeling chemically reacting flow in anode-supported solid-oxide fuel cells ͑SOFC͒. Depending on materials and operating conditions, SOFC anodes afford a possibility for internal reforming or catalytic partial oxidation of hydrocarbon fuels. An important new element of the model is the capability to represent elementary heterogeneous chemical kinetics in the form of multistep reaction mechanisms. Porous-media transport in the electrodes is represented with a dusty-gas model. Charge-transfer chemistry is represented in a modified Butler-Volmer setting that is derived from elementary reactions, but assuming a single rate-limiting step. The model is discussed in terms of systems with defined flow channels and planar membrane-electrode assemblies. However, the underlying theory is independent of the particular geometry. Solid oxide fuel cells ͑SOFC͒ can be operated with a variety of fuels, including hydrogen, CO, hydrocarbons, or mixtures of these. This is possible because of the relatively high operating temperatures, and, at least in conventional SOFC anodes, the use of transition metal catalysts that promote the water-gas-shift reactionand steam reforming, which for methane may be written globally asIf sufficient steam is produced electrochemically at the anode/ electrolyte interface by the reactionthen reforming and shifting can, in principle, lead to full ͑if indirect͒ electrochemical oxidation of a hydrocarbon fuel. However, competing reaction pathways catalyzed by transition metals may also lead to solid carbon deposition, which can quickly destroy the anode. For this reason, some degree of upstream fuel processing, eiher by catalytic partial oxidation or by steam reforming, is usually used to produce a fuel stream that is rich in H 2 and CO and dilute in residual hydrocarbons before reaching the SOFC. Because upstream processing adds to the complexity, size, and cost of the overall plant, it is of considerable interest to minimize or even eliminate the need for it. There is evidence that mixing some oxygen with a hydrocarbon fuel can deliver good performance.1 In this case there must be partial oxidation within the anode structrue. Another promising alternative to utilize hydrocarbon fuels "directly" in SOFCs is to use a ceria oxidation catalyst instead of a transition metal. 2Whether an SOFC uses a "reforming anode" with a transition metal catalyst, or a "direct oxidation" anode with a ceria-based catalyst, or perhaps uses a different, novel anode design, optimizing the system to run efficiently on hydrocarbon or hydrocarbon-derived fuels is a very challenging problem, due to the complex, coupled physico-chemical processes involved. When significant CO and/or hydrocarbons are present in the fuel, models must also account for the in situ production of hydrogen through reforming and shifting reactions within the anode, as well as solid-carbon formation.Many questions of interest for optimization studies cannot currently be answered easily. For example, for...

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“…The FVM code used in this study is MICROFOAM, which is a suitably modified version of the open-source computational fluid dynamics (CFD) code OpenFOAM ® [62]. The effective transport properties can be exploited in cell-level models of SOFCs to simulate transport in the porous electrodes [63][64][65][66][67][68][69]. In addition, the computational grids developed in this work along with the associated reconstructed microstructures can also be used to perform detailed microscopic simulations of SOFCs [3,20,70].…”

Section: Introductionmentioning

confidence: 99%

Effective transport properties of the porous electrodes in solid oxide fuel cells

Choi

Berson

Pharoah

et al. 2011

Proceedings of the Institution of Mechanical Engineers, Part A:

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This article presents a numerical framework for the computation of the effective transport properties of solid oxide fuel cells (SOFCs) porous electrodes from three-dimensional (3D) constructions of the microstructure. Realistic models of the 3D microstructure of porous electrodes are first constructed from measured parameters such as porosity and particle size distribution. Then each phase in the model geometries is tessellated with a computational grid. Three different types of grids are considered: Cartesian, octree, and body-fitted/cut-cell with successive levels of surface refinement. Finally, a finite volume method is used to compute the effective transport properties in the three phases (pore, electron, and ion) of the electrode. To validate the numerical approach, results obtained with the finite volume method are compared to those calculated with a random walk simulation for the case of a body-centred cubic lattice of spheres. Then, the influence of the sample size is investigated for random geometries with monosized particle distributions. Finally, effective transport properties are calculated for model geometries with polydisperse particle size distributions similar to those observed in actual SOFC electrodes.

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Simulation of a composite cathode in solid oxide fuel cells

Cited by 162 publications

References 27 publications

Modeling of a solid oxide electrolysis cell for carbon dioxide electrolysis

Modeling of a solid oxide electrolysis cell for carbon dioxide electrolysis

Modeling Elementary Heterogeneous Chemistry and Electrochemistry in Solid-Oxide Fuel Cells

Effective transport properties of the porous electrodes in solid oxide fuel cells

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