Electrochemical Potential Fluctuation Matters in Rate Constant Calculations for Proton-Coupled Electron Transfer

Area of Science:

• Electrochemistry
• Computational Chemistry
• Materials Science

Background:

• Proton-coupled electron transfer (PCET) reactions are fundamental to electrochemical energy conversion.
• Accurate rate constants are essential for understanding reaction mechanisms and designing electrocatalysts.
• Simulating constant potential conditions in grand canonical (GC) ensembles remains a challenge.

Purpose of the Study:

• To compare two distinct simulation strategies for introducing applied potentials in PCET reactions.
• To evaluate the impact of different potential treatments on calculated reaction rate constants.
• To determine the necessity of capturing instantaneous potential fluctuations in dynamic simulations.

Main Methods:

• Comparison of two simulation approaches: sampling GC ensemble with potential fluctuations versus fixing potential by adjusting electron numbers.
• Utilizing the Bennett-Chandler approach for calculating rate constants.
• Modeling the Volmer reaction on a Pt(111) surface as a test case.

Main Results:

• The two simulation strategies yielded different thermal activation and dynamic recrossing behaviors.
• Non-negligible differences in predicted reaction rate constants were observed between the two methods.
• The importance of including instantaneous potential fluctuations was demonstrated.

Conclusions:

• The choice of simulation method for applied potentials significantly impacts the predicted dynamics and kinetics of electrochemical PCET reactions.
• Accurately capturing instantaneous potential fluctuations is crucial for reliable dynamic simulations.
• This work provides critical insights for developing accurate computational methods for electrocatalysis research.