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Neutron imaging of fuel cells: retrospective and future work
Neutron imaging has been used since nearly 15 years [1-3] for the in situ imaging and quantification of water in operating fuel cells. The major interest of this method is the high penetration of neutrons through conventional fuel cell construction materials (e.g. aluminum, graphite, stainless steel) combined to the high sensitivity to water. Neutron imaging can be used in the conventional “through plane” configuration, where the neutron beam axes is perpendicular to the fuel cell membrane. In this configuration, the water distribution over the cell area is imaged, but the different layers of the cell cannot be distinguished. Another possible method is “in plane” imaging where the beam axis is parallel to the fuel cell membrane. There, the different layers of the fuel cell can be resolved, provided that the spatial resolution is sufficient. At the Paul Scherrer Institute, a set of resolution enhancement methods particularly focused on the application to fuel cell were developed [4, 5], which are based on the fact that the highest special resolution is only required in the direction across the cell structure.
In this talk, the basics of neutron imaging and its application to fuel cell will first be presented. After this, a restrospective will be given about how neutron imaging has helped us understand problems related to water management in the past years, including the impact of flow field design [2, 6], materials [3, 7] and sub-zero startup [8]. The role played by neutron imaging in our recent development of novel materialsfor fuel cells [9] will also be presented. Finally, an outlook will be given about future developments of the neutron imaging method for fuel cells, with a particular focus on the used of energy selective neutron imaging for the distinction of liquid water and ice [10].
[1] D. Kramer, E. Lehmann, G. Frei, et al., Nucl Instrum Meth A 542, 52 (2005).
[2] D. Kramer, J. Zhang, R. Shimoi, et al., Electrochim Acta 50, 2603 (2005).
[3] J. Zhang, D. Kramer, R. Shimoi, et al., Electrochim Acta 51, 2715 (2006).
[4] P. Boillat, D. Kramer, B.C. Seyfang, et al., Electrochem Commun 10, 546 (2008).
[5] P. Boillat, G. Frei, E.H. Lehmann, G.G. Scherer and A. Wokaun, Electrochem Solid St 13, B25 (2010).
[6] P. Stahl, J. Biesdorf, P. Boillat, J. Kraft and K.A. Friedrich, J Electrochem Soc 162, F677 (2015).
[7] J. Biesdorf, A. Forner-Cuenca, T.J. Schmidt and P. Boillat, J Electrochem Soc 162, F1243 (2015).
[8] P. Oberholzer, P. Boillat, R. Siegrist, et al., J Electrochem Soc 159, B235 (2012).
[9] A. Forner-Cuenca, J. Biesdorf, L. Gubler, et al., Advanced Materials 27, 6317 (2015).
[10] J. Biesdorf, P. Oberholzer, F. Bernauer, et al., Phys Rev Lett 112, 248301 (2014).
Pierre Boillat obtained his degree in Micro-engineering from the Swiss Federal Institute of Technology of Lausanne (EPFL) in 1997. After several years of work as an engineer in product development, he started working as a doctoral student at the Paul Scherrer Institute (PSI) on the topic of neutron imaging of fuel cells in 2005, and obtained his PhD degree for the Swiss Federal Institute of Technology of Zürich (ETHZ) in 2009. Since then, he has been working at PSI on the same topic – with a 6 month research stay at the Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA) in Grenoble (France) dedicated to studies with in situ small angle neutron scattering (SANS) of fuel cells. He is currently leading a research group at PSI having as main research axes the application of neutron imaging to electrochemical systems (fuel cells, electrolysers, batteries), the development of complementary characterization methods, and the development of novel fuel cell material and designs for optimized water management.
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