Comparison of Redox Potentials in Non-Aqueous Solvents: Silver is Not a Noble Metal in the Acidic Ionic Liquid HmimBr

Abstract

We recently introduced the concept of the Protoelectric Potential Map (PPM) which presents a new combined pH- and redox scale in an absolute sense.1,2 The two scales are thermodynamically well described and are based on the absolute chemical potential of the proton (m abs(H+)) and the absolute chemical potential of the electron (m abs (e-)) which at standard conditions are the standard Gibbs energy of solvation Dsolv G°(H+,S) and Dsolv G°(e–,S), resp. The PPM allows the quick comparison of redox potentials (reducities) and the pH values of any redox/acid-base system in any media which may lead to completely new insights and applications.

Basic Remarks on Acidity

“…This behavior means that in acidified [C 6 MIM]Br,silver is not aprecious metal because it dissolves concomitant with the generation of hydrogen gas. [79] TheAg + ion is stabilized better in the IL than, for example,i nw ater due to the formation of [AgBr 2 ] À ions.…”

“…An impressive example constitutes the redox system Ag + /Ag in [C 6 MIM]Br, which crosses the hydrogen line at pH abs =201 (green line, number 7). This behavior means that in acidified [C 6 MIM]Br, silver is not a precious metal because it dissolves concomitant with the generation of hydrogen gas . The Ag + ion is stabilized better in the IL than, for example, in water due to the formation of [AgBr 2 ] − ions.…”

Grundlegende Bemerkungen zur Azidität

“…7). Dies bedeutet, dass in angesäuertem [C 6 MIM]Br Silber unedel ist, da es unter H 2 ‐Entwicklung aufgelöst wird . Das Ag + ‐Ion wird in der IL aufgrund der Bildung von [AgBr 2 ] − ‐Ionen besser stabilisiert als z.…”