Microstructural Modeling and Effective Properties of Infiltrated SOFC Electrodes

Bertei, Antonio; Pharoah, Jon G.; Gawel, Duncan; Nicolella, Cristiano

doi:10.1149/05701.2527ecst

Cited by 13 publications

(7 citation statements)

References 15 publications

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“…Major differences between these three types of electrode arise when comparing TPB and DPB densities. As shown in Table 1, the impregnated Ni/CGO anode shows a TPB density of 41.6 lm À2 , which is roughly one order of magnitude larger than in the cermet 1 (5.0 lm À2 ), in agreement with previous investigations [42] and theoretical predictions [9]. The larger TPB density in impregnated electrodes compared with cermets is due to the much smaller Ni particle size (<50 nm vs 500 nm).…”

Section: Eis and Morphology Of Conventional Electrodessupporting

confidence: 88%

Model-guided design of a high performance and durability Ni nanofiber/ceria matrix solid oxide fuel cell electrode

Ouyang

Bertei

Cooper

et al. 2021

Journal of Energy Chemistry

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Mixed ionic electronic conductors (MIECs) have attracted increasing attention as anode materials for solid oxide fuel cells (SOFCs) and they hold great promise for lowering the operation temperature of SOFCs. However, there has been a lack of understanding of the performance-limiting factors and guidelines for rational design of composite metal-MIEC electrodes. Using a newly-developed approach based on 3D-tomography and electrochemical impedance spectroscopy, here for the first time we quantify the contribution of the dual-phase boundary (DPB) relative to the three-phase boundary (TPB) reaction pathway on real MIEC electrodes. A new design strategy is developed for Ni/gadolinium doped ceria (CGO) electrodes (a typical MIEC electrode) based on the quantitative analyses and a novel Ni/CGO fiber-matrix structure is proposed and fabricated by combining electrospinning and tape-casting methods using commercial powders. With only 11.5 vol% nickel, the designer Ni/CGO fiber-matrix electrode shows 32% and 67% lower polarization resistance than a nano-Ni impregnated CGO scaffold electrode and conventional cermet electrode respectively. The results in this paper demonstrate quantitatively using real electrode structures that enhancing DPB and hydrogen kinetics are more efficient strategies to enhance electrode performance than simply increasing TPB.

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Section: Eis and Morphology Of Conventional Electrodessupporting

confidence: 88%

Model-guided design of a high performance and durability Ni nanofiber/ceria matrix solid oxide fuel cell electrode

Ouyang

Bertei

Cooper

et al. 2021

Journal of Energy Chemistry

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“…The effective conductivity of backbone and infiltrated particles along with the effective diffusivity in gas phase are calculated and reported in dimensionless form to provide generality in their application. The study represents the extension of a previous work, 35 with additional results regarding the dependency of effective properties on the contact angle among nanoparticles and the backbone porosity.…”

mentioning

confidence: 80%

A Particle-Based Model for Effective Properties in Infiltrated Solid Oxide Fuel Cell Electrodes

Bertei

Pharoah

Gawel

et al. 2014

J. Electrochem. Soc.

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A modeling framework for the numerical reconstruction of the microstructure of infiltrated electrodes is presented in this study. A particle-based sedimentation algorithm is used to generate the backbone, while a novel packing algorithm is used to randomly infiltrate nanoparticles on the surface of backbone particles. The effective properties, such as the connected triple-phase boundary length, the effective conductivity, the effective diffusivity, are evaluated on the reconstructed electrodes by using geometric analysis, finite volume and random-walk methods, and reported in dimensionless form to provide generality to the results. A parametric study on the effect of the main model and operating parameters is performed. Simulations show that the critical loading (i.e., the percolation threshold) increases as the backbone porosity decreases and the nanoparticle diameter increases. Large triple-phase boundary length, specific surface area and good effective conductivity can be reached by infiltration, without detrimental effects on the effective transport properties in gas phase. Simulations reveal a significant sensitivity to the size and contact angle of infiltrated particles, suggesting that the preparation process of infiltrated electrodes should be properly tailored in order to obtain the optimized structures predicted by the model. In the last decade, much attention has been drawn toward nanostructured electrodes for solid oxide fuel cells (SOFCs) prepared via infiltration techniques.1-7 The main reason is reduced polarization resistance, with corresponding increased power density, in comparison with conventional electrodes prepared via traditional mixing and sintering processes. The improved performance of infiltrated electrodes holds even at intermediate temperatures (500-800• C), as demonstrated by a large number of experimental studies. [8][9][10][11][12][13] Other technological advantages are a wide choice of catalyst materials, a good adhesion and a reduced thermal expansion mismatch between the electrode and the electrolyte.3 On the other hand, the long-term stability and the fabrication cost of nanostructured electrodes still need to be properly addressed. 2,3The infiltration (or impregnation) technique involves the deposition of nanoparticles into a pre-sintered backbone of micrometer-size particles.1,3 The backbone is a skeletal structure typically composed of a single component, such as yttria-stabilized zirconia (YSZ) 5,8 or, in alternative, a mixed ionic-electronic conductor (e.g., lanthanum strontium cobalt ferrite LSCF).14 However, composite backbones, such as the usual lanthanum strontium manganite (LSM)/YSZ cathode, have also been used. 1,15 The sintering of the backbone is performed at high temperature in order to ensure structural stability of the electrode and good connection among backbone particles. 3 In the following step, nanoparticles are infiltrated in the backbone using different methods (such as metal salt precipitation, 2 nanoparticle dispersion, 16 molten salts) 1 and then sinte...

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“…Such a high TPB density value is caused by small Ni particles that attach to the large YSZ skeleton, which is similar to the principle of an SOFC electrode that infiltrates small nanoparticles into the large backbone. 32 A significant increase of TPB density means an enormous reduction of activity loss according to Butler-Volmer equation.…”

Section: Extracting Microstructures and Analysismentioning

confidence: 99%

Topology optimization of microstructure of solid‐oxide fuel cell anode to minimize thermal mismatch

Yong

Chai

et al. 2020

Int J Energy Res

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Summary Thermomechanical reliability and lifetime of solid‐oxide fuel cells are significantly influenced by thermal mismatch between anode and electrolyte layers. This study presents a numerical analysis of topology optimization of the microstructure of Ni–8YSZ anode to minimize the thermal mismatch of the components. We obtain two 2D microstructures by taking minimum thermal mismatch as object function. The 3D microstructures become fibrous and orthogonal by stretching the 2D microstructures. Results show that the coefficients of thermal expansion of microstructures in the plane parallel to the electrolyte layer are almost equal to those of electrolytes from room temperature to 800°C, which almost completely removes the thermal mismatch. Both microstructures have high three‐phase boundary density, which is almost twice or five times that of a typical anode. Compared with the typical anodes, the microstructures have higher Ni–pore interfacial areas and ion conductivities. Optimization results are helpful in the design of future electrodes.

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Microstructural Modeling and Effective Properties of Infiltrated SOFC Electrodes

Cited by 13 publications

References 15 publications

Model-guided design of a high performance and durability Ni nanofiber/ceria matrix solid oxide fuel cell electrode

Model-guided design of a high performance and durability Ni nanofiber/ceria matrix solid oxide fuel cell electrode

A Particle-Based Model for Effective Properties in Infiltrated Solid Oxide Fuel Cell Electrodes

Topology optimization of microstructure of solid‐oxide fuel cell anode to minimize thermal mismatch

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