Thermogalvanic cells demonstrate inherent physiochemical limitations in redox-active electrolytes at water-in-salt concentrations

Mark A. Buckingham, Kristine Laws, Huanxin Li, Yafei Kuang, Leigh Aldous*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

The majority of usable energy generated by humanity is lost as waste heat, but thermogalvanic systems (or thermocells) can address this problem by converting low-grade waste heat directly into electricity using redox chemistry. The concentration of the redox couple is a critical parameter; almost invariably, higher concentrations result in more power. This study exploits the simple synergy between Na+ and K+ counter ions to achieve—to the best of our knowledge—the most concentrated stable aqueous ferricyanide/ferrocyanide thermocell to date, at 1.6 m [Fe(CN)6]3−/4−. Despite increasing the concentration by 400% relative to the standard K3/K4[Fe(CN)6] electrolyte (0.4 m), electrical power production increased only 166%. Pushing the system from conventional salt-in-water electrolytes into the quasi-stable water-in-salt region (up to 2.4 m) resulted in a decrease in power. Detailed characterization highlighted the various physicochemical hurdles introduced by these extremely concentrated electrolytes; the identified issues have direct relevance to other energy systems also seeking to use the highest possible concentration.

Original languageEnglish
Article number100510
JournalCell Reports Physical Science
Volume2
Issue number8
DOIs
Publication statusPublished - 18 Aug 2021

Keywords

  • electrochemistry
  • energy harvesting
  • redox-active electrolytes
  • sustainable energy
  • thermocell
  • thermoelectrochemistry
  • thermogalvanic
  • water-in-salt electrolyte

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