Lithium interaction with nitrogen molecules trapped in defective multilayer graphene

Effect of carbon on the interaction of lithium with highly stable nitrogen molecule requires study for practical use in energy storage and electrochemical nitrogen reduction. In this work, we consider the interaction of lithium with nitrogen molecules embedded in defective multilayer graphene using synchrotron X-ray spectroscopy. Multilayer graphene synthesized by chemical vapor deposition was bombarded with 1 keV nitrogen ions to create lattice defects and insert ∼10 at.% nitrogen, and then used for lithium vapor deposition. All modifications of the graphene sample were carried under ultra-high vacuum conditions and accompanied by measurements of X-ray photoelectron and near-edge X-ray absorption fine structure spectra. Analysis of the spectra revealed the formation of intercalated N₂ molecules as a result of bombardment of graphene and their covalent interaction with deposited lithium. According to density functional theory calculations, the valence orbitals of N₂ and Li hybridize with the π-orbitals of graphene, which increases the bonding between the intercalants. This finding provides new insights into the processes occurring in N₂-intercalated graphene-based electrode materials during lithiation and can be used to develop efficient lithium-based electrochemical energy storage systems and electrochemical approaches for N₂ reduction reaction.