Theoretical and experimental study of the synthesis of nitrogen-doped graphene by graphene oxide and melamine.*

In this study, we achieved nitrogen-doped graphene by applying a post-treatment synthesis method take as precursors graphene oxide and melamine. Graphene oxide (GO) is synthesized by the modified Hummers method, which promotes the presence of epoxy, hydroxyl, and a few more functional groups. The samples were characterized by the XPS, UV-vis, and Bohem titration and the results show the presence of expected functional groups. The nitrogen-doped graphene is obtained by heating the samples of GO under 700°C in the presence of melamine mixed in water at different levels of acidic media. Through experimental adjustments in the concentration of oxygen species within graphene oxide, achieved by modifying key parameters like the edge-area ratio of the initial materials and the synthesis reaction temperature, we were able to confirm which specific groups promote the formation of a singular nitrogen species. By DFT calculations, we investigate the mechanism to form nitrogen-doped graphene. We calculated the desorption energies of the O-based functional groups, also, we performed NEB calculations to calculate the minimum energy pathways in the N-doped process.

We thank, DGAPA-UNAM projects IA100624, and IN101523. Calculations were performed in the DGCTIC-UNAM project no. LANCAD-UNAM-DGTIC-422.