First Principles Studies of Nitrogen Doped Carbon Nanotubes for Dioxygen Reduction

We performed first principles spin polarized density functional theory (DFT) calculations to simulate the nitrogen substitutionally doped short (10, 0) carbon nanotubes (CNTs) for dioxygen adsorption and reduction. Our calculated results show that nitrogen prefers to stay at the open-edge of the short CNTs. Dioxygen O-2 can adsorb and partially reduce on the carbon-nitrogen complex site (Paining site) and on carbon-carbon long bridge sites at the open-edge of the CNTs. The results of the spin polarization Calculations show that the carbon atoms on the open-edge of the CNT can possess a magnetic moment of about 0.59 mu B/atom, while those carbon atoms in the inner wall of the CNT do not have a magnetic moment. The doped nitrogen in the CNT does not have it magnetic moment. The chemisorption of dioxygen O-2 on the open-edge of the short CNT reduces the magnetic moments of the carbon atoms to nearly zero.