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Unravelling ionic speciation and hydration structure of Fe(III/II) redox couples for thermoelectrochemical cells

Title
Unravelling ionic speciation and hydration structure of Fe(III/II) redox couples for thermoelectrochemical cells
Authors
Kim, KyungguHwang, SunwookLee, Hochun
DGIST Authors
Kim, Kyunggu; Hwang, Sunwook; Lee, Hochun
Issue Date
2020-03
Citation
Electrochimica Acta, 335, 135651
Type
Article
Article Type
Article
Author Keywords
Thermoelectrochemical cellIron perchlorateRedox coupleSeebeck coefficientHydration structure
Keywords
REACTION ENTROPIESTHERMOGALVANIC CELLSHEATTHERMOCELLSELECTRODESCONVERSIONCHLORIDEPOWERNANOTUBESOLVENT
ISSN
0013-4686
Abstract
Thermoelectrochemical cells (TECs) are promising devices for harvesting heat waste, but their widespread use has been hindered by their low thermopower densities. High-power TECs require an electrolyte solution that exhibits both high Seebeck coefficient (Se) and high ionic conductivity; thus far, this has been a challenge. Recently, we demonstrated that proper selection of the counter anion of Fe(III)/(II) salts can resolve the aforementioned issue, that n-type (positive Se) TECs employing the Fe(III)/(II) perchlorate redox couple display unprecedented high areal power densities compared to TECs employing Fe(III)/(II) chloride or Fe(III)/(II) sulfate couple. Herein, we unravel that the excellent performance of the Fe(III)/(II) perchlorate is ascribed to the non-coordinating nature of its perchlorate anion, which suppresses the formation of the ion pairs that reduce the Se and ionic conductivity. UV–Vis and dielectric relaxation analysis revealed that the redox reaction of the hexa aquo complexes (Fe(H2O)6 3+/2+), formed Fe(III)/(II) perchlorate, is accompanied by a hydration-number change larger than those of anion-coordinated species, which are dominant in chloride or sulfate media. In addition, n-type TECs can be combined in-series with p-type (negative Se) TECs to provide output powers high enough for practical application. © 2020 Elsevier Ltd
URI
http://hdl.handle.net/20.500.11750/11423
DOI
10.1016/j.electacta.2020.135651
Publisher
Pergamon Press Ltd.
Related Researcher
  • Author Lee, Hochun Electrochemistry Laboratory for Sustainable Energy(ELSE)
  • Research Interests Lithium-ion batteries; Novel Materials for rechargeable batteries; Novel energy conversion;storage systems; Electrochemistry; 리튬이차전지; 이차전지용 신규 전극 및 전해액; 신규 에너지변환 및 저장 시스템; 전기화학
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Collection:
Department of Energy Science and EngineeringElectrochemistry Laboratory for Sustainable Energy(ELSE)1. Journal Articles


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