Excess heat production in the redox couple reaction of ferricyanide and ferrocyanide

Atsushi Sugiyama*, Makoto Miura, Yoshinobu Oshikiri, Yena Kim, Ryoichi Morimoto, Miki Miura, Tetsuya Osaka, Iwao Mogi, Yusuke Yamauchi*, Ryoichi Aogaki*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


In order to establish the universality of the excess heat production in electrochemical reaction, under a high magnetic field, as one of the most fundamental electrochemical reactions, the case of ferricyanide-ferrocyanide redox reaction was examined, where ionic vacancies with ± 1 unit charge were collided by means of magnetohydrodynamic (MHD) flow. As a result, from the pair annihilation of the vacancies with opposite signs, beyond 7 T, excess heat production up to 25 kJ·mol−1 in average at 15 T was observed, which was attributed to the liberation of the solvation energy stored in a pair of the vacancy cores with a 0.32 nm radius, i.e., 112 kJ·mol−1. Difference between the observed and expected energies comes from the small collision efficiency of 0.22 due to small radius of the vacancy core. Ionic vacancy initially created as a by-product of electrode reaction is unstable in solution phase, stabilized by releasing solvation energy. Ionic vacancy utilizes the energy to enlarge the core and stores the energy in it. As a result, solvated ionic vacancy consists of a polarized free space of the enlarged core surrounded by oppositely charged ionic cloud. The accuracy and precision of the measured values were ascertained by in situ standard additive method.

Original languageEnglish
Article number20072
JournalScientific reports
Issue number1
Publication statusPublished - 2020 Dec
Externally publishedYes

ASJC Scopus subject areas

  • General


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