Absolute Potentials of the Standard Hydrogen Electrode (4.20 V), Standard Reference Electrodes & Aqueous Redox Couples of Elements
Authors: Heyrovska Raji 
Published: February 2020

For more than two centuries after Volta (1745 – 1827) (http://www.ecsblog.org/the-birthplace-of-electrochemistry), aqueous redox potentials have been conventionally referred to that of the standard hydrogen electrode (SHE) as zero, in the absence of a proper knowledge of the latter. The author demonstrated for the first time (Heyrovska, 2009) a new simple linear relation between the gaseous ionization potentials (I) and the aqueous standard redox potentials (E0) using the existing data for the elements of various Groups in the Periodic Table. It was astonishing that all these straight lines converged to one point at I = 0, yielding the absolute potential of SHE, E0
I=0 = 4.20 (+/- 0.03)V.
This value was found to be close to the theoretical value (4.44V) obtained earlier by Trasatti (1986) (Pure & Appl. Chem. 58 (1986) 955) and to the experimental value, 4.2 (+/-0.4V) obtained by Donald et al, (2008) (J. Am. Chem. Soc. 130 (2008) 3371). Thus, by knowing the absolute value of SHE, the absolute aqueous redox potentials, Eo
abs = Eo - Eo
I =0, of all the elements of the Periodic Table (Heyrovska, 2010) as well as of the standard reference electrodes were obtained and tabulated (Heyrovska, 2009, 2010, 2011). Full list of references in: http://www.jh-inst.cas.cz/~rheyrovs/publs.htm. Some selected references are given below.

References

1. Absolute Potentials of the Hydrogen Electrode and of Aqueous Redox Couples
R. Heyrovska,
Electrochemical and Solid-State Letters, 12(10) (2009) F29-F30.
2. Absolute aqueous redox potentials (via a new link between aqueous and gaseous properties)
R. Heyrovska, 1) 9th workshop of physical chemists and electrochemists, Brno, June 2009; http://www.chemi.muni.cz/~libuse/setkani2009/index.html
2) http://precedings.nature.com/documents/3395/version/1 (2009).
3. Aqueous Redox Potentials Found to be Inversely Proportional to the Bohr Radius
R. Heyrovska, 1) 216th ECS Meeting, Vienna, Austria, October 2009: Electrochem. Soc. 902, 3067, 2009. (Abstract); 2) http://ecsmeet6.peerx-press.org/ms_files/ecsmeet6/2009/04/24/00004143/00/4143_0_art_0_k6mfy4_cnvpdf.pdf ; 3) Electrochem. Soc. Trans., 25, (2010) 159-163.
4. Absolute potentials of standard reference electrodes at 25 0C
R. Heyrovska, 1) MEM 2009 conference, dedicated to Prof. J. Heyrovsky on the occasion of the 50th Anniversary of the award of the Nobel Prize for Polarography, Prague, 9-13 December 2009: http://www.natur.cuni.cz/heyrovsky; 2) Conference Proceedings: Chemicke Listy, 103 (2009) OP-10, s238: http://www.chemicke-listy.cz ;
3) Proceedings of the Modern Electroanalytical Methods 2009, 13-Prague, Czech Republic, 9- December 2009, Department of Chemistry, Faculty of Science, Charles University, Editors: J. Barek, K. Nesmìrák,OP-10, page 10 in: http://web.natur.cuni.cz/heyrovsky/Heyrovsky2009 Proceedings complete.pdf ;
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R. Heyrovska, Electroanalysis, 22 (Issue 9), (2010) 903 - 907, Published online; 4 March 2010.