MESA+ University of Twente
Inorganic Materials Science Group

Research

Background

picture 1The SOFC technology has reached a very high level of refinement over the last decades. Large stationary power plants incorporating SOFC stacks have been demonstrated throughout the world with impressive technical results. However, the cost of the state-of-the-art SOFC technology remains too high to compete with entrenched power generation technologies. As a consequence there is an increasing interest over the last ten years in the development of metal supported SOFC (MSC), which is expected to be competitive in the power generation equipment market because of strength, tolerance to extreme rapid thermal cycling and reduced materials costs that metal supports provide. The main technological hurdle for the introduction of the MSC is the cost efficient depositing of a defect free thin film electrolyte layer on such metal support [1-3].

Abstract

The purpose of this project concerns the development of a cheap and easily upscalable technology for thin film electrolytes for solid oxide fuel cells (SOFC) and solid oxide electrolyser cells (SOEC), e.g., yttria-stabilized zirconia, and gadolinia doped ceria, on porous steel and optionally dense substrates. Because of these demands the attention will be focused primarily on the development of a wet-chemical route. Here one should think about the use of sol-gel techniques and chemical solution deposition, i.e., techniques with which a wet film with the proper molar ratio of cations can be deposited at room temperature. Techniques such as dip coating, spin coating and misted deposition will be employed to deposit films (~5 cm2 surface area and a thickness of 2-5 micron). Flame assisted spray pyrolysis will be considered as alternative. The advantage of this set of techniques is that they all employ similar kinds of precursor solutions and they are all suited for both planar and non-planar substrates. Although upscaling and production issues are not part of this project, the fabrication techniques that will be considered should potentially allow upscaling and economical production.

An important issue in this project concerns the thermal consolidation of the dried films. Both conventional techniques and microwave-based rapid thermal annealing techniques will be employed. The latter technique has the additional advantage that the thermal consolidation step is very fast, and it is possible to sinter dense films at much lower temperatures than is possible with conventional sintering, and the microstructure can be controlled well.

All above-mentioned techniques have a broad parameter space, which renders the development and optimization time-consuming and labour-intensive. For this reason physical deposition, e.g., pulsed laser deposition, will be used in the optimization process, in order to screen parts of the parameter space quickly. The sintered films will be tested with gas tightness tests to determine the defectivity of the layers. High temperature electrochemical impedance spectroscopy will be employed to characterize the ionic conductivity of the layers (sheet resistance for oxygen ions transport of less than 0.15 W cm2 at 600°C).

References

1.

R. Hui, Z. Wang, O. Kesler, L. Rose, J. Jankovic, S. Yick, R. Maric and D. Ghosh, Thermal plasma spraying for SOFCs: Applications, potential advantages, and challenges, J. Power Sources 130 (2007) 308-323.

2.

S. Hui, D. Yang, Z. Wang, S. Yick, C. Deces-Petit, W. Qu, A. Tuck, R. Maric, and D. Ghosh, Metal supported solid oxide fuel cell operated at 400-600°C, J. Power Sources, 167 (2007) 336-339.

3.

A. Saiki, Y. Fujisawa, T. Hashizume, and K. Terayama, Yttria Stabilized Zirconia Thin Films Formation From an Aqueous Solution by Mist Deposition, Ceramic Trans. 195 (2006) 115-124.

PhD student: Sjoerd Veldhuis

Daily Supervisor: Andre ten Elshof