We introduce the protoelectric potential map (PPM) as a novel, two-dimensional plot of the absolute reduction potential (peabs scale) combined with the absolute protochemical potential (Brønsted acidity: pHabs scale). The validity of this thermodynamically derived PPM is solvent-independent due to the scale zero points, which were chosen as the ideal electron gas and the ideal proton gas at standard conditions. To tie a chemical environment to these reference states, the standard Gibbs energies for the transfer of the gaseous electrons/protons to the medium are needed as anchor points. Thereby, the thermodynamics of any redox, acid-base or combined system in any medium can be related to any other, resulting in a predictability of reactions even over different media or phase boundaries. Instruction is given on how to construct the PPM from the anchor points derived and tabulated with this work. Since efforts to establish "absolute" reduction potential scales and also "absolute" pH scales already exist, a short review in this field is given and brought into relation to the PPM. Some comments on the electrochemical validation and realization conclude this concept article.

Metals often are classified as “noble” or “base”—characterizing their reduction potential as one of the most important chemical properties. We show that metals are only as noble as allowed by their environment, i.e. this is a relative term, and the “frame of reference” simply is the solvent in which the redox system is present. We prove that silver is a prime example for a noble metal that forfeits its noble character in the simple ionic liquid HMIM Br (1-hexyl-3-methylimidazolium bromide) as an example for such a solvent.

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.

S Redoxpotenziale und pH-Werte lassen sich nur innerhalb desselben Mediums sinnvoll miteinander vergleichen. Der Grund dafür ist, dass sowohl die Nernst-Gleichung als auch die Sørensen' sche pH-Gleichung relative chemische Potenziale redoxaktiver Spezies bzw. Protonen enthalten. Nötig wären aber Definitionen auf der Basis der absoluten chemischen Potenziale von Elektronen und Protonen.Für Brønstedsäuren leistet dies eine im Jahr 2010 eingeführte absolute pH-Skala. 1) Die Definition des absoluten pH-Werts als erlaubt es, Aziditäten (Säurestärken) von Protonen in unterschiedlichen chemischen Umgebungen direkt zu vergleichen, da das chemische Potenzial des Protons im Medium (H + , Medium) eben direkt von dieser Umgebung -dem Mediumabhängt. Um Vergleichbarkeit zu erreichen, ist dem chemischen Potenzial ein universeller, also von jeglichem Medium unabhängiger, Energie-oder Skalen-Nullpunkt zuzuweisen. Dieser Nullpunkt wird auf das chemische Potenzial des Protons in einem idealen Protonengas unter Standardbedingungen von 1 bar und 298,15 K festgelegt. Dieser Referenzzustand ist der hypothetische Zustand maximaler Azidität der Protonen.Ein Protonengas mit dem Druck 10 -200 bar erhält so einen pH abs -

We define both, the Redox Potential scale and the pH scale of Brønsted acids in a novel manner. These definitions are based on the absolute chemical potential of the electron and of the proton, resp. The resulting quantities – the Absolute Reducity peabs and the Absolute Acidity pHabs – are absolute in the sense that they are medium independent. The plot of both scales against each other results in the Protoelectric Potential Map (PPM) and enables the straightforward comparability of the thermochemistry of any redox, acid-base or combined system in any medium to any other