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 Cu(2)–N(6)/Gr, Cu(2)–N(8)/Gr and Cu–N(4)/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 Cu(2)–N(6)/Gr and Cu(2)–N(8)/Gr are more stable structure-wise, while free energy calculations showed that only Cu(2)–N(8)/Gr and Cu–N(4)/Gr structures support spontaneous ORR. The maximum cell potential under standard conditions was shown at 0.28 V and 0.49 V for Cu(2)–N(8)/Gr and Cu–N(4)/Gr respectively. From the calculations, the Cu(2)–N(6)/Gr and Cu(2)–N(8)/Gr structures are less favorable in H(2)O(2) generation; however, Cu–N(4)/Gr showed the potential for H(2)O(2) generation. In conclusion, Cu(2)–N(8)/Gr and Cu–N(4)/Gr are more favorable to ORR than Cu(2)–N(6)/Gr.