Seminar : Bernhard Roling (Department of Chemistry, University of Marburg) – Friday 10 February 2023 at 11am (room 32-42.101)

Published on : 19/01/2023

Classifying Electrolyte Solutions by Comparing Charge and Mass Transport

Berhard Roling

Friday 10 May 2023 at 11am (room 32-42.101)


Electrolyte solutions play an important role in many scientific fields, such as electrochemistry, energy research, chemical synthesis, biochemistry and pharmaceutical research [1-4]. The conventional classification of electrolyte solutions as “strong” or “weak” accounts for their charge transport properties, but neglects their mass transport properties, and is not readily applicable to highly concentrated solutions.
Here we use the Onsager transport formalism in combination with linear response theory to attain a more general classification, which is based on a comparison of charge and mass transport [5, 6]. Charge transport is characterized by the ionic conductivity σ𝑖𝑜𝑛 and mass transport by the neutral salt transport coefficient σ𝑠𝑎𝑙𝑡. Three classes of electrolyte solutions are then distinguished [5,6]: (i) “Strong electrolytes” with σ𝑖𝑜𝑛≈σ𝑠𝑎𝑙𝑡; (ii) “weak charge transport electrolytes” with σ𝑖𝑜𝑛≪σ𝑠𝑎𝑙𝑡; and (iii) “weak mass transport electrolytes” with σ𝑠𝑎𝑙𝑡≪σ𝑖𝑜𝑛. While classes (i) and (ii) encompass the classical “strong” and “weak” electrolytes, respectively, many highly concentrated electrolytes fall into class (iii) and thus exhibit transport properties clearly distinct from classical strong and weak electrolytes.
[1] H.-P. Landolt, S. C. Holst, Science 2016, 352, 517.
[2] Z. Zhang, J. Song, and B. Han, Chem. Rev. 2017, 117, 6834.
[3] M. Watanabe, M. L. Thomas, S. Zhang, K. Ueno, T. Yasuda, K. Dokko, Chem. Rev. 2017, 117, 7190.
[4] M. Li, C. Wang, Z. Chen, K. Xu, J. Lu, Chem. Rev. 2020, 120, 6783.
[5] B. Roling, J. Kettner, V. Miß, Energy Environ. Mater. 2022, 5, 6.
[6] B. Roling, V. Miß, J. Kettner, Energy Environ. Mater. 2022, e12533.
doi: 10.1002/eem.12553