Asymmetric Marcus-Hush theory for voltammetry

Area of Science:

• Electrochemistry
• Physical Chemistry
• Chemical Physics

Background:

• The Butler-Volmer and Marcus-Hush models are widely used for electron transfer modeling.
• Experimental data often deviates from predictions made by these ubiquitous models for redox couples.
• These discrepancies highlight limitations in the simplifying assumptions of current models.

Purpose of the Study:

• To review the state-of-the-art in modeling electron transfer rates.
• To identify the shortcomings of existing models in accurately reproducing experimental voltammetry.
• To explore refined models that better capture the complexities of electron transfer.

Main Methods:

• Review of experimental studies on electron transfer kinetics.
• Analysis of deviations from the Butler-Volmer and Marcus-Hush models.
• Examination of asymmetric models with varied vibrational and solvation parameters.
• Investigation of the non-adiabatic electron transfer assumption.

Main Results:

• Neither the Butler-Volmer nor the symmetric Marcus-Hush models fully explain experimental voltammetry.
• Experimental data for both solution-phase and surface-bound redox couples show significant deviations.
• Asymmetric models and consideration of non-adiabatic effects provide improved accuracy.
• Refined models enable more detailed microscopic characterization through electrochemical measurements.

Conclusions:

• Existing simplified models for electron transfer are insufficient.
• Incorporating asymmetry and non-adiabaticity leads to more accurate modeling.
• Advanced models enhance understanding of microscopic system characteristics via electrochemistry.