https://doi.org/10.1140/epje/s10189-024-00408-9
Regular Article - Soft Matter
Local electroneutrality breakdown for electrolytes within varying-section nanopores
1
Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich, Erlangen, Germany
2
Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franqués 1, 08028, Barcelona, Spain
3
Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, 08028, Barcelona, Spain
4
Department of Chemical and Biological Engineering and Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
Received:
15
November
2023
Accepted:
25
January
2024
Published online:
19
February
2024
We determine the local charge dynamics of a 
electrolyte embedded in a varying-section channel. By means of an expansion based on the length scale separation between the axial and transverse direction of the channel, we derive closed formulas for the local excess charge for both, dielectric and conducting walls, in 2D (planar geometry) as well as in 3D (cylindrical geometry). Our results show that, even at equilibrium, the local charge electroneutrality is broken whenever the section of the channel is not homogeneous for both dielectric and conducting walls as well as for 2D and 3D channels. Interestingly, even within our expansion, the local excess charge in the fluid can be comparable to the net charge on the walls. We critically discuss the onset of such local electroneutrality breakdown in particular with respect to the correction that it induces on the effective free energy profile experienced by tracer ions.
© The Author(s) 2024
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