Modeling interfacial electron transfer using path integral molecular dynamics

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Outer sphere electron transfer (OSET) rates are crucial in many chemical and biological processes.
• Current methods often simplify electron transfer as instantaneous charge changes, potentially limiting accuracy.
• Accurate simulation of electron transfer is essential for understanding redox reactions and designing new materials.

Purpose of the Study:

• To develop and implement a novel methodology for calculating OSET rates using an explicit path-integral representation of the electron.
• To compare the accuracy of this explicit method against traditional implicit methods.
• To investigate the influence of distance, applied potential, and spectator cations on OSET rates.

Main Methods:

• Combining path integral molecular dynamics (PIMD) with Marcus-Hush-Chidsey (MHC) theory.
• Simulating electron transfer from a ferrocyanide complex to a gold electrode.
• Analyzing the dependence of transfer rates on electron transfer distance and applied potential.
• Investigating the role of bridging spectator cations.

Main Results:

• The explicit path-integral electron model yields OSET rates and thermodynamics more consistent with experimental findings than implicit models.
• The methodology accurately captures the dependence of rates on distance and applied potential.
• Specific cation effects on electron transfer rates were observed and found to be more consistent with experimental data using the path-integral approach.

Conclusions:

• An explicit path-integral electron representation offers a more accurate approach to simulating OSET rates.
• This method provides better agreement with experimental observations, particularly regarding thermodynamic properties and cation effects.
• The developed methodology is a valuable tool for studying electron transfer in complex systems.