Seminar professor Robert Dryfe

SEMINAR
Electrochemistry: beyond the comfort zone
Robert Dryfe (University of Manchester, UK)
Wednesday 29th April, 11:00, Amphi 2, ENSMAC

The “default” electroanalytical chemistry experiment typically uses supporting electrolyte at concentrations on the order of 0.1 M. However, many “real” electrochemical systems use much higher, or sometimes much lower, concentrations. Concentrated electrolyte phases are particularly interesting because they often behave in very different ways to dilute electrolytes. Certain simple salts (e.g. KF) as well as more complex organic based salts (such as the lithium salt of the Bis(trifluoromethanesulfonyl)azanide – or TFSI – anion) are soluble in water to ca. 20 molal concentrations at room temperature. These “water-in-salt” phases have attracted attention as potential battery electrolytes, however, there are a number of more fundamental aspects that are not fully explored. To give some examples: concentrated LiTFSI phases form immiscible (aqueous bi-phases) with concentrated salts of LiCl [1]. They are also capable of “salting in” organic solutes, which are normally insoluble in pure water [2,3]. Their physical properties, for example the concentration dependence of the contact angle on (e.g.) carbon electrodes, or the concentration dependence of the interfacial tension in the aqueous bi-phase case mentioned above, have not been explored in detail [4]. A further aspect of interest is how to measure meaningful electrode potentials in concentrated electrolyte phases, noting that significant liquid-junction potentials are likely to exist [5].
I will present aspects of our experimental programme on the bulk and surface properties of certain “water-in-salt” electrolytes. Our experimental work is performed in tandem with molecular dynamics simulations, in an attempt to give atomic scale insight into some of the unusual phenomena observed [6].
Finally, concentrated electrolytes also present the ideal playground for electrowetting studies, where graphite has been identified as an ideal substrate. This is the potential-dependence of the contact angle of a liquid electrolyte on a solid substrate (electrode); we have re-evaluated the classical Young-Lippmann methodology that has been used, hitherto, to interpret electrowetting data [7].

References:
1. N. Dubouis et al, J. Phys. Chem. B, 125, (2021), 5365
2. H.M. Burnett et al, ACS Electrochemistry, 1, (2025), 1821
3. S. Kishioka, Electroanalysis, 35, (2023), e02300171.
4. P. Iamprasertkun et al, Chem. Sci., 11, (2020), 6978.
5. D. Degoulange et al, J. Chem. Phys., 155, (2021), 064701.
6. H.O. Wood et al, Faraday Disc., 253, (2024), 212.
7. A.A. Papaderakis et al, J. Amer. Chem. Soc., 145, (2023), 8007.