Redox Levels through Constant Fermi-Level ab Initio Molecular Dynamics.

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Electrochemistry

Background:

• Determining redox potentials is crucial for understanding and designing electrochemical systems.
• Traditional methods may require prior knowledge of reaction products, limiting their applicability.
• Accurate theoretical prediction of redox levels is essential for advancing catalysis and energy storage.

Purpose of the Study:

• To introduce a novel method for calculating redox levels of half reactions.
• To model electrode effects by controlling charge transfer with a constant Fermi energy.
• To provide a computationally efficient and accurate alternative to existing methods.

Main Methods:

• Utilizing ab initio molecular dynamics evolving at constant Fermi energy.
• Simulating charge transfer between system energy levels and an electron reservoir.
• Extracting redox levels from Kohn-Sham energy evolution during charging/discharging.
• Applying Janak's theorem and assuming quadratic energy evolution.

Main Results:

• The developed method accurately determines redox levels for half reactions.
• Simulations were performed for Fe2+/Fe3+, HO2•/HO2-, and MnO4-/MnO4-2 redox couples in aqueous solution.
• Redox potentials obtained were within 0.1 eV of those from the thermodynamic integration method.
• The scheme does not require a priori knowledge of reaction products.

Conclusions:

• The ab initio molecular dynamics method at constant Fermi energy is a viable approach for redox potential determination.
• This method offers an accurate and efficient alternative to thermodynamic integration.
• The approach is general and applicable to various redox systems in solution.