Nitrogen-tuned bonding mechanism of Li and Ti adatom embedded graphene

• Nitrogen defects changed the bonding mechanism between metal and graphene.
• Bonding character and binding results were investigated using DFT calculations.
• Covalent bonding character occurred around pyridinic and pyrrolic N-doped graphene.
• Pyridinic and pyrrolic N atoms are effective for metal dispersion on the graphene.

The effects of nitrogen defects on the bonding mechanism and resultant binding energy between the metal and graphene layer were investigated using density functional theory (DFT) calculations. For the graphitic N-doped graphene, Li adatom exhibited ionic bonding character, while Ti adatom showed features of covalent bonding similar to that of pristine graphene. However, in the cases of pyridinic and pyrrolic structures, partially covalent bonding characteristic occurred around N atoms in the process of binding with metals, and this particular bond formation enhanced the bond strength of metal on the graphene layer as much as it exceeded the cohesive energy of the metal bulk. Thus, Li and Ti metals are expected to be dispersed with atomic accuracy on the pyridinic and pyrrolic N-doped graphene layers. These results demonstrate that the bonding mechanism of metal–graphene complex can change according to the type of N defect, and this also affects the binding results.

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