Confinement-Modulated Proton-Transfer Kinetics in Graphene and Graphene-Oxide Nanochannels: A Markovian Statistical...

Area of Science:

• Physical Chemistry
• Materials Science
• Nanotechnology

Background:

• Ångström-scale confinement significantly alters water's properties, including dielectric response and proton transport.
• Microscopic kinetics of proton transfer in confined water remain poorly understood despite experimental observations.

Purpose of the Study:

• To quantitatively resolve proton-transfer kinetics between hydroxide and water in graphene nanochannels.
• To establish a statistical framework linking atomistic dynamics to emergent transport phenomena.

Main Methods:

• Reactive molecular dynamics (ReaxFF MD) and ab initio molecular dynamics (AIMD) simulations.
• Continuous-time Markovian statistical framework analyzing waiting-time distributions.
• Investigation of pristine and functionalized graphene nanochannels.

Main Results:

• Proton hopping follows a memoryless Markov process with a well-defined rate constant on picosecond timescales.
• Nanoconfinement accelerates proton transfer by 2-4 times compared to bulk water, reducing activation energy.
• Graphene oxide defects and functional groups further enhance proton transfer via interfacial electric fields and catalytic hotspots.

Conclusions:

• Microscopic kinetic trends provide a mechanistic basis for enhanced dielectric response and fast proton transport in confined systems.
• Confinement-induced reactivity, dielectric anomalies, and ion transport in low-dimensional aqueous systems are better understood.
• A general statistical framework for atomistic proton-transfer dynamics is established.