Presolvation Dynamics Preceding the Hydrated Proton Transfer in the Electrical Double Layer

Area of Science:

• Physical Chemistry
• Electrochemistry
• Materials Science

Background:

• Proton transfer (PT) mechanisms in solid-liquid electric double layers (EDLs) are complex due to potential-dependent solvation structures.
• Understanding these mechanisms is crucial for applications in energy storage and catalysis.

Purpose of the Study:

• To investigate the influence of operating potential on hydrated proton transfer mechanisms within an EDL.
• To elucidate how potential affects solvation structure, hydrogen bonding, and proton diffusion.

Main Methods:

• Combined the fixed-potential method with ab initio molecular dynamics (AIMD) simulations.
• Simulated proton transfer under a constant potential framework.

Main Results:

• Negative potentials promote proton diffusion by reducing trapping but stiffen the hydrogen bond network, restricting water orientation.
• At high negative potentials, Eigen cations ((H2O)3H3O+) form, exhibiting higher PT energy barriers than pentamers ((H2O)4H3O+).
• Stiffening effects and Eigen cation formation suppress proton conductivity near the electrode surface.

Conclusions:

• The operating potential significantly modulates PT mechanisms in EDLs.
• Potential-induced structural changes, including hydrogen bond stiffening and cation formation, are key factors limiting proton conductivity.
• This study provides fundamental insights into interfacial proton transport phenomena.