Interplay between solvent effects of different nature in interfacial bond breaking electron transfer

Area of Science:

• Electrochemistry
• Physical Chemistry
• Chemical Physics

Background:

• The electroreduction of peroxodisulphate is a key bond-breaking electron transfer reaction.
• Understanding solvent dynamics is crucial for interpreting electrochemical reaction rates.

Purpose of the Study:

• To explore solvent dynamics effects on peroxodisulphate anion electroreduction using the Sumi-Marcus model.
• To provide a new interpretation of reaction survival times and explain experimental viscosity dependencies.

Main Methods:

• Construction of a 3D free energy surface via the Anderson model Hamiltonian.
• Incorporation of Pekar factor changes due to varying solution concentrations (viscosity).
• Application of the Sumi-Marcus model to analyze solvent and intramolecular contributions.

Main Results:

• Model calculations successfully interpret experimental data showing non-monotonic rate constants versus solution viscosity.
• The influence of mixed solvent composition on reaction rate and transfer coefficient is explained.
• Saddle point avoidance near activationless discharge is identified as a key factor.

Conclusions:

• Splitting reaction coordinates into slow (solvent) and fast (intramolecular) is essential for accurate modeling.
• Simplified models fail to capture critical reaction features, even when addressing static and dynamic effects.
• The Sumi-Marcus model provides a robust framework for understanding complex electrochemical reactions.