Absolute Potentials of the Standard Hydrogen Electrode (4.20 V), Standard Reference Electrodes & Aqueous Redox Couples of Elements

Abstract

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.