Fluctuationenhanced electric conductivity in electrolyte solutions
In this work, we analyze the effects of an externally applied electric field on thermal fluctuations for a binary electrolyte fluid. We show that the fluctuating Poisson–Nernst–Planck (PNP) equations for charged multispecies diffusion coupled with the fluctuating fluid momentum equation result in enhanced charge transport via a mechanism distinct from the wellknown enhancement of mass transport that accompanies giant fluctuations. Although the mass and charge transport occurs by advection by thermal velocity fluctuations, it can macroscopically be represented as electrodiffusion with renormalized electric conductivity and a nonzero cation–anion diffusion coefficient. Specifically, we predict a nonzero cation–anion Maxwell– Stefan coefficient proportional to the square root of the salt concentration, a prediction that agrees quantitatively with experimental measurements. The renormalized or effective macroscopic equations are different from the starting PNP equations, which contain no crossdiffusion terms, even for rather dilute binary electrolytes. At the same time, for infinitely dilute solutions the renormalized electric conductivity and renormalized diffusion coefficients are consistent and the classical PNP equations with renormalized coefficients are recovered, demonstrating the selfconsistency of the fluctuating hydrodynamics equations. Our calculations show that the fluctuating hydrodynamics approach recovers the electrophoretic and relaxation corrections obtained by Debye–Huckel–Onsager theory, while elucidating the physical origins ofmore »
 Authors:

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 Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Computational Research Division
 New York Univ. (NYU), NY (United States). Department of Mathematics, Courant Institute of Mathematical Sciences
 San Jose State University, CA (United States). Department of Physics and Astronomy
 Publication Date:
 Grant/Contract Number:
 AC0205CH11231; SC0008271
 Type:
 Published Article
 Journal Name:
 Proceedings of the National Academy of Sciences of the United States of America
 Additional Journal Information:
 Journal Volume: 114; Journal Issue: 41; Related Information: © 2017, National Academy of Sciences. All rights reserved.; Journal ID: ISSN 00278424
 Publisher:
 National Academy of Sciences, Washington, DC (United States)
 Research Org:
 Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
 Sponsoring Org:
 USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC21)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 97 MATHEMATICS AND COMPUTING; fluctuating hydrodynamics; electrohydrodynamics; Navier–Stokes equations; multicomponent diffusion; Nernst–Plank equations
 OSTI Identifier:
 1396062
 Alternate Identifier(s):
 OSTI ID: 1426738
Péraud, JeanPhilippe, Nonaka, Andrew J., Bell, John B., Donev, Aleksandar, and Garcia, Alejandro L.. Fluctuationenhanced electric conductivity in electrolyte solutions. United States: N. p.,
Web. doi:10.1073/pnas.1714464114.
Péraud, JeanPhilippe, Nonaka, Andrew J., Bell, John B., Donev, Aleksandar, & Garcia, Alejandro L.. Fluctuationenhanced electric conductivity in electrolyte solutions. United States. doi:10.1073/pnas.1714464114.
Péraud, JeanPhilippe, Nonaka, Andrew J., Bell, John B., Donev, Aleksandar, and Garcia, Alejandro L.. 2017.
"Fluctuationenhanced electric conductivity in electrolyte solutions". United States.
doi:10.1073/pnas.1714464114.
@article{osti_1396062,
title = {Fluctuationenhanced electric conductivity in electrolyte solutions},
author = {Péraud, JeanPhilippe and Nonaka, Andrew J. and Bell, John B. and Donev, Aleksandar and Garcia, Alejandro L.},
abstractNote = {In this work, we analyze the effects of an externally applied electric field on thermal fluctuations for a binary electrolyte fluid. We show that the fluctuating Poisson–Nernst–Planck (PNP) equations for charged multispecies diffusion coupled with the fluctuating fluid momentum equation result in enhanced charge transport via a mechanism distinct from the wellknown enhancement of mass transport that accompanies giant fluctuations. Although the mass and charge transport occurs by advection by thermal velocity fluctuations, it can macroscopically be represented as electrodiffusion with renormalized electric conductivity and a nonzero cation–anion diffusion coefficient. Specifically, we predict a nonzero cation–anion Maxwell– Stefan coefficient proportional to the square root of the salt concentration, a prediction that agrees quantitatively with experimental measurements. The renormalized or effective macroscopic equations are different from the starting PNP equations, which contain no crossdiffusion terms, even for rather dilute binary electrolytes. At the same time, for infinitely dilute solutions the renormalized electric conductivity and renormalized diffusion coefficients are consistent and the classical PNP equations with renormalized coefficients are recovered, demonstrating the selfconsistency of the fluctuating hydrodynamics equations. Our calculations show that the fluctuating hydrodynamics approach recovers the electrophoretic and relaxation corrections obtained by Debye–Huckel–Onsager theory, while elucidating the physical origins of these corrections and generalizing straightforwardly to more complex multispecies electrolytes. Lastly, we show that strong applied electric fields result in anisotropically enhanced “giant” velocity fluctuations and reduced fluctuations of salt concentration.},
doi = {10.1073/pnas.1714464114},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 41,
volume = 114,
place = {United States},
year = {2017},
month = {9}
}