Lu, X;
Antonio, B;
Jason, C;
Heenan, TMM;
Mohamad, R;
Li, K;
DANIEL, B;
(2018)
The application of hierarchical structures in energy devices: new insights into the design of solid oxide fuel cells with enhanced mass transport.
Energy and Environmental Science
, 11
pp. 2390-2403.
10.1039/C8EE01064A.
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Abstract
Mass transport can significantly limit the rate of reaction and lead to concentration polarisation in electrochemical devices, especially under the conditions of high operating current density. In this study we investigate hierarchically structured micro-tubular solid oxide fuel cells (MT-SOFC) fabricated by a phase inversion technique and quantitatively assess the mass transport and electrochemical performance improvement compared to a conventional tubular SOFC. We present pioneering work to characterise the effective mass transport parameters for the hierarchically porous microstructures by an integrated computed fluid dynamics simulation, assisted by multi-length scale 3D X-ray tomography. This has been historically challenging because either imaging resolution or field of view has to be sacrificed to compensate for the wide pore size distribution, which supports different transport mechanisms, especially Knudsen flow. Results show that the incorporation of radially-grown micro-channels helps to decrease the tortuosity factor by approximately 50% compared to the conventional design consisting of a sponge-like structure, and the permeability is also improved by two orders of magnitude. When accounting for the influence of Knudsen diffusion, the molecule/wall collisions yield an increase of the tortuosity factor from 11.5 (continuum flow) to 23.4 (Knudsen flow), but the addition of micro-channels helps to reduce it down to 5.3. Electrochemical performance simulations using the measured microstructural and mass transport parameters show good agreement with the experimental results at elevated temperatures. The MT-SOFC anode displays 70% lower concentration overpotential, 60% higher power density (0.98 vs. 0.61 W cm−2) and wider current density window for maximum power density than the conventional design.
| Type: | Article |
|---|---|
| Title: | The application of hierarchical structures in energy devices: new insights into the design of solid oxide fuel cells with enhanced mass transport |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1039/C8EE01064A |
| Publisher version: | https://doi.org/10.1039/C8EE01064A |
| Language: | English |
| Additional information: | This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10055842 |
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