Nitrogen Doping Enables Covalent-Like π-π Bonding between Graphenes

Area of Science:

• Materials Science
• Chemistry
• Condensed Matter Physics

Background:

• Bilayer graphenes typically exhibit van der Waals (vdW) interactions between layers.
• Layer separation in pristine graphene is governed by these weak vdW forces.

Purpose of the Study:

• To investigate a novel chemical bonding in nitrogen-doped graphenes (NGPs).
• To explore the formation of unusual 2D π-π bonding in bilayer NGPs.
• To quantify the impact of this bonding on interlayer separation and binding energy.

Main Methods:

• Rigorous theoretical calculations.
• Electronic structure calculations.
• Crystal Orbital Overlap Population (COOP) analyses.

Main Results:

• N-doped graphenes (NGPs) form unusual 2D π-π bonding in bilayers, reducing interlayer separation.
• Interlayer binding energies are enhanced by up to 50% compared to pristine graphene bilayers.
• This covalent-like bonding arises from π-π overlap while maintaining planar, in-plane π-conjugation.

Conclusions:

• The study reveals a new aspect of graphene chemistry with N-doped graphenes.
• The enhanced interlayer bonding in NGPs leads to unique material properties.
• Optimally doped NGP-based graphite exhibits metallic characteristics in both in-plane and stacking directions.