Hydrogenation Facilitates Proton Transfer through Two-Dimensional Honeycomb Crystals.

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Chemistry

Background:

• Experimental studies suggest facile proton transfer through graphene and hexagonal boron nitride (h-BN) layers.
• Theoretical calculations indicate high energy barriers (>3 eV) for proton penetration, creating a discrepancy.
• The origin of this experimental-computational anomaly remains unexplained.

Purpose of the Study:

• To investigate the discrepancy between experimental observations and theoretical predictions of proton transfer barriers in graphene and h-BN.
• To elucidate the underlying mechanism responsible for facile proton transport.
• To provide a new perspective reconciling experimental findings with computational models.

Main Methods:

• First-principles calculations were employed to simulate proton penetration through single-layer graphene and h-BN.
• The effect of hydrogenation on the proton penetration barrier was specifically analyzed.
• Analysis focused on changes in the initial state and lattice structure upon hydrogenation.

Main Results:

• Calculations reveal that hydrogenation significantly reduces the proton penetration barrier to <1 eV, even without lattice defects like pinholes.
• Hydrogenation destabilizes the initial chemisorption state of protons.
• The honeycomb lattice expands due to hydrogenation, facilitating proton passage.

Conclusions:

• Hydrogenation provides a plausible explanation for the experimentally observed fast proton transfer through graphene and h-BN.
• This mechanism rationalizes the anomaly between experimental data and prior simulations.
• Highlights the potential for efficient proton transport in single-layer materials within hydrogen-rich environments.