Aqueous Proton Transportation in Graphene-Based Nanochannels.

Area of Science:

• Materials Science
• Computational Chemistry
• Physical Chemistry

Background:

• Graphene oxide (GO) exhibits high proton conductivity, making it suitable for proton conduction nanochannels.
• Understanding proton transport in confined environments is crucial for designing advanced energy devices.

Purpose of the Study:

• To investigate the influence of confinement and surface chemistry on proton transport in graphene-based nanochannels.
• To elucidate the mechanisms governing proton and water molecule behavior within these nanochannels.

Main Methods:

• Extensive ReaxFF Molecular Dynamics (MD) simulations were performed.
• Graphene (GE), graphane (GA), and hydroxygraphane (HG) sheets were used to model different surface chemistries.
• Nanochannels with varying interlayer distances were simulated.

Main Results:

• Confinement stratifies water molecules, with orientation dictated by surface chemistry, affecting proton distribution.
• Graphene (GE) channels under extreme confinement show crushed hydrogen-bond networks, favoring ultrafast vehicle-mechanism proton transport.
• Functional groups in graphane (GA) and hydroxygraphane (HG) maintain more complete hydrogen-bond networks, facilitating Grotthuss hopping of protons.

Conclusions:

• Proton transport mechanisms in graphene-based nanochannels are critically dependent on interlayer distance and surface functionalization.
• Surface chemistry modulates water structure and hydrogen-bond networks, influencing the dominant proton transport pathway (vehicle vs. Grotthuss).
• Findings provide guidance for designing efficient proton exchange membranes and other proton conduction devices.