Voltammetric Perspectives on the Acidity Scale and H⁺/H₂ Process in Ionic Liquid Media

Area of Science:

• Electrochemistry
• Physical Chemistry
• Materials Science

Background:

• Nonhaloaluminate ionic liquids (ILs) are increasingly used as alternatives to molecular solvents.
• Understanding how IL properties affect electrochemical reactivity is crucial for their application.
• Proton (H+) transfer and H+/H2 reactions are fundamental electrochemical processes.

Purpose of the Study:

• To review recent voltammetric studies on proton transfer energetics and H+/H2 reaction mechanisms in ILs.
• To discuss the influence of IL structure on electrochemical reactivity.
• To highlight the need for systematic investigations into IL structure-property relationships.

Main Methods:

• Voltammetric studies were used to investigate electrochemical processes.
• The pKa formalism was employed to quantify proton transfer energetics.
• Electrode reaction mechanisms, specifically the H+/H2 process, were analyzed.

Main Results:

• Proton transfer energetics (pKa) are strongly dependent on the IL anion and, to a lesser extent, the cation.
• The H+/H2 process, an inner-sphere reaction, exhibits IL-dependent electrochemical characteristics.
• Electrochemical reactivity is significantly modulated by the specific ionic liquid formulation.

Conclusions:

• The choice of IL anion and cation critically impacts proton transfer and H+/H2 reaction energetics.
• Ionic liquid properties profoundly influence electrochemical reaction mechanisms.
• Systematic studies are essential to establish structure-function relationships for optimizing ILs in electrochemical applications.