Materials Colloquium 2021, September 1st


Fuel cells, batteries, electrolyzers, etc.: some insights from a materials science point of view

Lorenz Gubler (Electrochemistry Laboratory – PSI)

Electrochemical storage & conversion technologies are expected to play a pivotal role in the energy transition and defossilization of our economy. In addition to batteries used for grid-scale energy storage and electromobility, electrochemical conversion devices using or producing hydrogen, i.e. fuel cells and electrolyzers, can contribute to reducing the carbon footprint of the transport sector and chemical industry. In this seminar, we will be looking at the state-of-the-art of these devices, and highlight selected challenges regarding the choice of cell materials and components. Examples from the research on these topics will be shown to illustrate current limitations of the technology and future prospects.

Do soft solids have strain-dependent surface tension?

Nicolas Bain (Soft and Living Materials – D-MATL)

Despite its importance in any adhesion and wetting phenomena, there is a fundamental property that is not yet understood in soft solids: surface elasticity. Also called the Shuttleworth effect, surface elasticity can be boiled down to one question. Does stretching the surface of a soft solid change its surface tension? In 2017, Xu et. al designed an experiment in which the opening angle of a wetting ridge was a proxy to evidence a dramatic increase of surface tension with stretch. In 2019, however, Masurel et al. claimed that the coupling between nonlinear mechanics and the singular nature of the wetting ridge suffice to explain the behavior of the opening angle observed by Xu et al, without invoking the Shuttleworth effect. The question, therefore, remains open. This presentation will focus on an experimental setup with no geometric singularity, that leaves no doubt on the existence or absence of surface elasticity in soft solids, hopefully closing this long-lasting controversy.

Q. Xu, K. E. Jensen, R. Boltyanskiy, R. Sarfati, R. W. Style, and E. R. Dufresne, Nature communications 8, 1 (2017).
R. Masurel, M. Roché, L. Limat, I. Ionescu, and J. Dervaux, Physical review letters 122, 248004 (2019).

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