Comparative study of adsorption of O_2, CO_2, NO_2 and SO_2 on pristine and Si-Doped Carbon Nanotubes

摘要

Density functional theory is used to investigate the adsorption properties of O_2, CO_2, SO_2 and NO_2 gas molecules on pristine carbon nanotube (CNT) and Si-doped carbon nanotube (Si-CNT). All molecules except NO_2 are physisorbed, with essentially no charge transfer between the CNT and molecules. The electronic properties of CNT are sensitive to the adsorption of NO_2 because of its chemisorption, while they are insensitive to the O_2, CO_2 and SO_2 molecules. The weak binding of these molecules on CNT is due to formation of charge-dipole interactions. In case of Si-CNT, all molecules are chemisorbed to the Si-C bonds with appreciable adsorption energy and significant charge transfer. The density of state analysis shows that the additional state near the Fermi level due to doping of silicon is responsible for chemisorption of the molecules. Further, our theoretical results suggest that molecule-induced modification of the density of states close to the Fermi level might significantly affect the transport properties of nanotubes.