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Title: On the hydrophilicity of electrodes for capacitive energy extraction

Authors:
; ; ;
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Fluid Interface Reactions, Structures and Transport Center (FIRST)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1388647
DOE Contract Number:
ERKCC61
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physics. Condensed Matter; Journal Volume: 28; Journal Issue: 46; Related Information: FIRST partners with Oak Ridge National Laboratory (lead); Argonne National Laboratory; Drexel University; Georgia State University; Northwestern University; Pennsylvania State University; Suffolk University; Vanderbilt University; University of Virginia
Country of Publication:
United States
Language:
English
Subject:
catalysis (heterogeneous), solar (fuels), energy storage (including batteries and capacitors), hydrogen and fuel cells, electrodes - solar, mechanical behavior, charge transport, materials and chemistry by design, synthesis (novel materials)

Citation Formats

Lian, Cheng, Kong, Xian, Liu, Honglai, and Wu, Jianzhong. On the hydrophilicity of electrodes for capacitive energy extraction. United States: N. p., 2016. Web. doi:10.1088/0953-8984/28/46/464008.
Lian, Cheng, Kong, Xian, Liu, Honglai, & Wu, Jianzhong. On the hydrophilicity of electrodes for capacitive energy extraction. United States. doi:10.1088/0953-8984/28/46/464008.
Lian, Cheng, Kong, Xian, Liu, Honglai, and Wu, Jianzhong. 2016. "On the hydrophilicity of electrodes for capacitive energy extraction". United States. doi:10.1088/0953-8984/28/46/464008.
@article{osti_1388647,
title = {On the hydrophilicity of electrodes for capacitive energy extraction},
author = {Lian, Cheng and Kong, Xian and Liu, Honglai and Wu, Jianzhong},
abstractNote = {},
doi = {10.1088/0953-8984/28/46/464008},
journal = {Journal of Physics. Condensed Matter},
number = 46,
volume = 28,
place = {United States},
year = 2016,
month = 9
}
  • The so-called Capmix technique for energy extraction is based on the cyclic expansion of electrical double layers to harvest dissipative energy arising from the salinity difference between freshwater and seawater. Its optimal performance requires a careful selection of the electrical potentials for the charging and discharging processes, which must be matched with the pore characteristics of the electrode materials. While a number of recent studies have examined the effects of the electrode pore size and geometry on the capacitive energy extraction processes, there is little knowledge on how the surface properties of the electrodes affect the thermodynamic efficiency. In thismore » paper, we investigate the Capmix processes using the classical density functional theory for a realistic model of electrolyte solutions. The theoretical predictions allow us to identify optimal operation parameters for capacitive energy extraction with porous electrodes of different surface hydrophobicity. Finally, in agreement with recent experiments, we find that the thermodynamic efficiency can be much improved by using most hydrophilic electrodes.« less
  • Capacitive double-layer expansion is a promising technology to harvest energy arising from the salinity difference between freshwater and seawater. Its optimal performance requires a careful selection of the operation potentials and electrode materials. While carbonaceous materials such as graphene and various forms of activated carbons are routinely used as the electrodes, there is little knowledge on how the quantum capacitance and the electric double-layer (EDL) capacitance, which are on the same order of magnitude, affect the capacitive performance. Toward understanding that from a theoretical perspective, here we study the capacitive energy extraction with graphene electrodes as a function of themore » number of graphene layers. The classical density functional theory is joined with the electronic density functional theory to obtain the EDL and the quantum capacitance, respectively. The theoretical results show that the quantum capacitance contribution plays a dominant role in extracting energy using the single-layer graphene, but its effect diminishes as the number of graphene layers increases. The overall extracted energy is dominated by the EDL contribution beyond about four graphene layers. Electrodes with more graphene layers are able to extract more energy at low charging potential. Here, because many porous carbons have nanopores with stacked graphene layers, our theoretical predictions are useful to identify optimal operation parameters for capacitive energy extraction with porous electrodes of different wall thickness.« less
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