Probing iron adsorption on the internal and external wall of pristine and N-doped carbon nanotube

Abstract

Herein, density functional theory (DFT) calculations were used to compare the interaction pattern of iron atoms on the internal and external wall of pristine and nitrogen-doped (6, 6) single walled carbon nanotubes. Among the four investigated cases, the interaction strength of Fe in ascending order follows 3Fe@CNT, 4Fe@N-CNT, 5Fe/CNT and 4Fe/N-CNT, where “/” and “@” indicate adsorption on the external and internal wall of CNT, respectively. The enhancement of N-doped surface can be ascribed to the activated carbon atoms neighbouring the dopant. The distortion analysis shows that both 3Fe@CNT and 4Fe@N-CNT adsorption system cause less structural distortion on the internal surface of the nanotube, while 4Fe/N-CNT system presents the largest distortion. Density of state analysis predicts that the metal atom inside and outside demonstrates distinct electronic properties and the internal metal particle shows a more dispersed bonding pattern with the carbon surface due to the concave nature of internal surface. The calculated dispersion energy for different adsorption systems provides more evidence for the delocalised interaction pattern, and 4Fe@N-CNT exhibits the largest dispersion interaction.