The adsorption of CO, O2 and H2 on Li–doped defective (8,0) SWCNT: A DFT study

Abstract

This work presents a theoretical study, based on DFT calculations, about the changes induced when diatomic molecules (CO, O2 and H2) are adsorbed on defective (8,0) SWCNT doped with a Li atom. The adsorption of one Lithium atom is tested inside and outside of the nanotube containing a single vacancy. The Li atom induces a magnetic moment on the nanotube and an important reduction in its the band gap (Eg). The adsorption energy values (Eads) for CO, O2 and H2 when Li is located inside, are higher than when Li is outside. The H2 adsorption does not change the magnetic nature of the system. However, the CO and O2 molecules reduce the magnetic moment from 1.0 µB to 0.0 µB. The band gap energy is reduced for CO and O2, while increases in the case of H adsorption. The work function (WF) value is reduced in the cases of CO and H2; whereas for O2 we observed an opposite behavior, then the final charge state of this molecule is negative. Based on our results, the system Li + defective (8,0) SWCNT can be proposed as possible candidate as gas sensor of CO,O2 and H2.