A DFT screening of CH4 detection by (8,0) single-walled carbon nanotubes decorated with small tin oxide clusters

Abstract

In this work, the structural, electronic and methane (CH₄) adsorption properties of (8,0)single-walled carbon nanotubes(SWCNTs) decorated with small tin oxide clusters were theoretically studied. The optimal adsorption orientations of adsorbates on (8,0)SWCNT and the adsorption energies were obtained. Our results show that tin oxide clusters were adsorbed on (8,0)SWCNT through an exothermic reaction with adsorption energies ranging from -491.937 to -739 meV. Moreover, the electronic properties of (8,0)SWCNT were modulated by the addition of tin oxide clusters to the host material. In particular, the energy band gap of SWCNT decreased when tin oxide clusters were included, presumably due to the nanotube bulging and charge migration from the former to the latter. The CH₄ adsorption process on decorated (8,0)SWCNT is exothermic and physical. Compared to its competitors, the Sn₄O₄-decorated (8,0)SWCNT releases the greatest energy when the CH₄ molecule is adsorbed, accompanied by a higher charge transfer from the latter to the former. We attribute the amelioration of the CH₄ adsorption property to the electrostatic dipole-dipole interaction induced by charge-density redistribution. Owing to the change in the electronic effective mass, the conductivity of all materials changes in the presence of the CH₄ molecule. Therefore, the decorated (8,0)SWCNTs can be used as a thermopower-based or resistance-based CH₄ sensor.