Cu - Nitrogen doped graphene (Cu-N/Gr) nanocomposite as cathode catalyst in fuel cells - DFT study

Novel Cu-nitrogen doped graphene nanocomposite catalysts are developed to investigate the Cu-nitrogen doped fuel cell cathode catalyst. Density functional theory calculations are performed using Gaussian 09w software to study the oxygen reduction reaction (ORR) on Cu-nitrogen doped graphene nanocomposite cathode catalyst in low-temperature fuel cells. Three different nanocomposite structures Cu₂-N₆/Gr, Cu₂-N₈/Gr and Cu-N₄/Gr were considered in the acidic medium under standard conditions (298.15 K, 1 atm) in order to explore the properties of the fuel cell. The results showed that all structures are stable at the potential range 0-5.87 V. Formation energy, Mulliken charge and HOMO-LUMO energy calculations showed that Cu₂-N₆/Gr and Cu₂-N₈/Gr are more stable structure-wise, while free energy calculations showed that only Cu₂-N₈/Gr and Cu-N₄/Gr structures support spontaneous ORR. The maximum cell potential under standard conditions was shown at 0.28 V and 0.49 V for Cu₂-N₈/Gr and Cu-N₄/Gr respectively. From the calculations, the Cu₂-N₆/Gr and Cu₂-N₈/Gr structures are less favorable in H₂O₂ generation; however, Cu-N₄/Gr showed the potential for H₂O₂ generation. In conclusion, Cu₂-N₈/Gr and Cu-N₄/Gr are more favorable to ORR than Cu₂-N₆/Gr.