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Title: Analysis of thermocapacitive effects in electric double layers under a size modified mean field theory

Abstract

Thermodynamics of the electric double layer has received renewed interest for its potential applications in low-grade waste heat harvesting and reversible heating/cooling in supercapacitors. We apply a size-modified mean field theory to analytically capture the influence on the pseudo-Seebeck coefficient S = ∂φ 0/∂T) σ of different factors, including the electrode potential φ 0, asymmetry in ion sizes, and ion concentration, under a fixed electrode surface charge σ. The pseudo-Seebeck coefficient is predicted to scale as φ 0/T at low electrode potentials, but it reaches limiting values when the electrode potential exceeds crossover values due to the steric effect. The qualitative behavior changes substantially, however, when the temperature dependence of the permittivity is taken into account. The pseudo-Seebeck coefficient S is then predicted to scale linearly with φ 0 even at high electrode potentials, significantly over-predicting the experimental values. Lastly, this suggests a strong influence of phenomena not captured in the mean field theory, such as deviation of local effective permittivity from the bulk value, thermally facilitated adsorption or desorption of ions on electrode surfaces, and weakening of ionic associations with temperature.

Authors:
ORCiD logo [1]
  1. Univ. of California, Los Angeles, CA (United States)
Publication Date:
Research Org.:
SRI International, Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
OSTI Identifier:
1510953
Alternate Identifier(s):
OSTI ID: 1402112
Grant/Contract Number:  
AR0000532
Resource Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 111; Journal Issue: 17; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING

Citation Formats

Ju, Y. Sungtaek. Analysis of thermocapacitive effects in electric double layers under a size modified mean field theory. United States: N. p., 2017. Web. doi:10.1063/1.5003362.
Ju, Y. Sungtaek. Analysis of thermocapacitive effects in electric double layers under a size modified mean field theory. United States. doi:10.1063/1.5003362.
Ju, Y. Sungtaek. Mon . "Analysis of thermocapacitive effects in electric double layers under a size modified mean field theory". United States. doi:10.1063/1.5003362. https://www.osti.gov/servlets/purl/1510953.
@article{osti_1510953,
title = {Analysis of thermocapacitive effects in electric double layers under a size modified mean field theory},
author = {Ju, Y. Sungtaek},
abstractNote = {Thermodynamics of the electric double layer has received renewed interest for its potential applications in low-grade waste heat harvesting and reversible heating/cooling in supercapacitors. We apply a size-modified mean field theory to analytically capture the influence on the pseudo-Seebeck coefficient S = ∂φ0/∂T)σ of different factors, including the electrode potential φ0, asymmetry in ion sizes, and ion concentration, under a fixed electrode surface charge σ. The pseudo-Seebeck coefficient is predicted to scale as φ0/T at low electrode potentials, but it reaches limiting values when the electrode potential exceeds crossover values due to the steric effect. The qualitative behavior changes substantially, however, when the temperature dependence of the permittivity is taken into account. The pseudo-Seebeck coefficient S is then predicted to scale linearly with φ0 even at high electrode potentials, significantly over-predicting the experimental values. Lastly, this suggests a strong influence of phenomena not captured in the mean field theory, such as deviation of local effective permittivity from the bulk value, thermally facilitated adsorption or desorption of ions on electrode surfaces, and weakening of ionic associations with temperature.},
doi = {10.1063/1.5003362},
journal = {Applied Physics Letters},
number = 17,
volume = 111,
place = {United States},
year = {2017},
month = {10}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Figures / Tables:

FIG. 1 FIG. 1: The predicted pseudo-Seebeck coefficient S as a function of the (initial) electrode potential. The solid line corresponds to the prediction from the GC theory and the dashed and dash-dotted lines from the SMFT theory for two different values of ξ.

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Works referenced in this record:

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.