Tortuosity of an SOFC anode estimated from saturation currents and a mass transport model in comparison with a real micro-structure

Brus, Grzegorz; Miyawaki, Kosuke; Iwai, Hiroshi; Saito, Motohiro; Yoshida, Hideo

doi:10.1016/j.ssi.2014.07.002

Cited by 49 publications

(28 citation statements)

References 27 publications

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“…In the absence of this information, effective transport properties of porous structures have been derived experimentally by means of diffusion cell experiments 16,17,[64][65][66][67][68][69][70] and electrochemical measurements. 15,19,46,71 …”

Section: Experimentally Derived Tortuositymentioning

confidence: 99%

Tortuosity in electrochemical devices: a review of calculation approaches

Tjaden

Brett

Shearing

2016

International Materials Reviews

211

188

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The tortuosity of a structure plays a vital role in the transport of mass and charge in electrochemical devices. Concentration polarisation losses at high current densities are caused by mass transport limitations and are thus a function of microstructural characteristics. As tortuosity is notoriously difficult to ascertain, a wide and diverse range of methods has been developed to extract the tortuosity of a structure. These methods differ significantly in terms of calculation approach and data preparation techniques. Here, we review tortuosity calculation procedures applied in the field of electrochemical devices to better understand the resulting values presented in the literature. Visible differences between calculation methods are observed, especially when using porosity-tortuosity relationships and when comparing geometric and flux based tortuosity calculation approaches.

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Section: Experimentally Derived Tortuositymentioning

confidence: 99%

Tortuosity in electrochemical devices: a review of calculation approaches

Tjaden

Brett

Shearing

2016

International Materials Reviews

211

188

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“…Studies have shown that differences between imaging, simulation and experimental-based calculation methods can amount to more than a factor of two (Tjaden et al, 2016b) and might only achieve agreement under certain conditions (e.g. at high concentration losses Brus et al, 2014). One reason for this may be that image-based techniques typically do not consider all of the transport phenomena during diffusive mass transport such as Knudsen effects and are inherently limited by the imaging resolution (Finegan et al, 2016).…”

Section: = 2 (1)mentioning

confidence: 99%

“…Hence, for quantitative analyses, the diffusion cell experimental approach provides a tortuosity value dominating under the current experimental conditions. These conditions, however, might have a substantial influence on the calculated tortuosity, as shown in (Brus et al, 2014): SOFC anode tortuosity values as low as 2 and above 12 were achieved depending on the injected fuel gas concentration and degree of concentration polarisation. As a consequence, following previous observations in literature (Tsai and Schmidt, 2011;Brus et al, 2014), it is expected that the tortuosity values presented in Table 5 will decrease to values similar to the ones calculated using flux-based approaches when the complete oxygen transport membrane is in operation under high fuel conversation ratios, where mass transport limitations become more dominating.…”

Section: Diffusion Cell-based Tortuositymentioning

confidence: 99%

“…These conditions, however, might have a substantial influence on the calculated tortuosity, as shown in (Brus et al, 2014): SOFC anode tortuosity values as low as 2 and above 12 were achieved depending on the injected fuel gas concentration and degree of concentration polarisation. As a consequence, following previous observations in literature (Tsai and Schmidt, 2011;Brus et al, 2014), it is expected that the tortuosity values presented in Table 5 will decrease to values similar to the ones calculated using flux-based approaches when the complete oxygen transport membrane is in operation under high fuel conversation ratios, where mass transport limitations become more dominating. Finally, the tortuosity values of samples PS 2.4 30.0% and PS 29-1.0 were compared to evaluate the effect of sample thickness on the tortuosity: both of these samples feature an almost identical porosity and mean pore diameter, making the thickness the distinguishing parameter.…”

Section: Diffusion Cell-based Tortuositymentioning

confidence: 99%

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Contradictory concepts in tortuosity determination in porous media in electrochemical devices

Tjaden

Finegan

Lane³

et al. 2017

Chemical Engineering Science

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Porous media are a vital component in almost every electrochemical device in the form of electrode, support or gas diffusion layers. Microstructural parameters of porous layers such as tortuosity, porosity and pore size diameter are of high importance and crucial for diffusive mass transport calculations. Among these parameters, the tortuosity remains ill-defined in the field of electrochemistry, resulting in a wide range of different calculation approaches. Here, we present a systematic approach of calculating the tortuosity of different porous samples using image and diffusion cell experimental-based methods. Image-based analyses include a selection of geometric and flux-based tortuosity calculation algorithms. Differences between the image and diffusion cell-based results are encountered and attributed to the small pore diameters and thereby induced Knudsen effects within the samples which govern the diffusion flux. Highlights Microstructural analysis of oxygen transport membrane porous supports.  Correlative tortuosity determinations via X-ray tomography and diffusion cell experiments.  Evaluation of the effect of tortuosity, porosity and sample thickness on diffusion resistance.  Visible differences between different tortuosity calculation approaches are encountered.  Diffusion cell experiments yield the highest and geometric-based image quantification algorithms result in the lowest tortuosity values.

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“…Berson et al [16] reported that Bruggeman correction, which was only valid for ε 0.6  , introduced big errors in low [15,[19][20][21][22][23][24][25][26][27], line + solid triangle symbols denote the results calculated by Equation (9), solid square symbols denote the results calculated by the 3D sphere packing model [17]. Figure 4 shows the dependence of fpε, τqp" D eff {D 0 q on porosity.…”

Section: Resultsmentioning

confidence: 99%

A Simple Expression for the Tortuosity of Gas Transport Paths in Solid Oxide Fuel Cells’ Porous Electrodes

Kong

Zhang

et al. 2015

Energies

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Based on the three-dimensional (3D) cube packing model, a simple expression for the tortuosity of gas transport paths in solid oxide fuel cells' (SOFC) porous electrodes is developed. The proposed tortuosity expression reveals the dependence of the tortuosity on porosity, which is capable of providing results that are very consistent with the experimental data in the practical porosity range of SOFC. Furthermore, for the high porosity (>0.6), the proposed tortuosity expression is also accurate. This might be helpful for understanding the physical mechanism for the tortuosity of gas transport paths in electrodes and the optimization electrode microstructure for reducing the concentration polarization.

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Tortuosity of an SOFC anode estimated from saturation currents and a mass transport model in comparison with a real micro-structure

Cited by 49 publications

References 27 publications

Tortuosity in electrochemical devices: a review of calculation approaches

Tortuosity in electrochemical devices: a review of calculation approaches

Contradictory concepts in tortuosity determination in porous media in electrochemical devices

A Simple Expression for the Tortuosity of Gas Transport Paths in Solid Oxide Fuel Cells’ Porous Electrodes

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