Bridging Hydration-Shell Exchange Kinetics and Ion Translocation Energy Barriers across Graphene Nanopores

Area of Science:

• Nanoscale science
• Physical chemistry
• Materials science

Background:

• Ion transport through angstrom-scale nanopores is crucial for applications like water desalination and energy storage.
• The energy barriers for ion translocation are influenced by water dynamics within the pore, but the precise kinetic origins remain unclear.

Purpose of the Study:

• To elucidate the kinetic origin of ion translocation energy barriers in graphene nanopores.
• To quantitatively link hydration shell dynamics to ion transport energy barriers.

Main Methods:

• Ionic conductance measurements to characterize graphene nanopore confinement.
• Molecular dynamics simulations to analyze hydration shell dynamics during ion translocation.
• Residence-time analysis to decompose water behavior into dehydration, exchange, and fluctuations.

Main Results:

• Established the angstrom-scale confinement regime of graphene nanopores.
• Quantitatively determined the number of irreversibly removed hydration waters during ion translocation.
• Demonstrated a monotonic increase in irreversible dehydration with the translocation energy barrier for K+ and Mg2+ ions.

Conclusions:

• Hydration shell exchange kinetics are the molecular-level determinants of ion transport barriers in angstrom-scale graphene nanopores.
• Provides a dynamically grounded and physically transparent understanding of ion transport under extreme nanoconfinement.