Parametrizing reaction probabilities for proton transfers in protic ionic liquids

Area of Science:

• Electrochemistry
• Computational Chemistry
• Materials Science

Background:

• Protic ionic liquids (PILs) are electrolytes with inherent proton conductivity.
• Understanding proton transfer in PILs is crucial for electrochemical applications.
• Quantitative data on proton transfer mechanisms in PILs is limited.

Purpose of the Study:

• To systematically investigate proton transfer in 1-methylimidazolium carboxylates using quantum mechanics.
• To parametrize reaction probabilities for reactive molecular dynamics simulations.
• To elucidate the factors governing proton transfer rates in these systems.

Main Methods:

• Density functional theory (DFT) scans to map potential energy surfaces.
• Analysis of relaxed potential energy surfaces along donor-acceptor distance and proton transfer coordinates.
• Fitting energy profiles with Morse potentials and reaction probabilities with hyperbolic tangent functions.

Main Results:

• Potential energy surfaces were accurately described by Morse potentials.
• Proton transfer reactions exhibited small or negligible energy barriers.
• Quantum tunneling effects were found to be minor.
• Reaction probabilities are primarily governed by thermally activated hopping.

Conclusions:

• Proton transfer in 1-methylimidazolium carboxylates is dominated by thermally activated hopping.
• The findings provide parameters for reactive molecular dynamics simulations.
• This work enhances the quantitative understanding of proton transfer in PIL electrolytes.