Adsorption mechanism of SO2 on vacancy-defected graphene and Ti doped graphene: A DFT study

The adsorption properties of SO2 on graphene surface are explored by means of first-principle calculations using the density functional theory. The four graphene structures involved in the calculation include pristine graphene (PG), vacancy-defected graphene (VG), Ti-doped graphene (Ti-G), and Ti-doped graphene with vacancies (Ti-VG). According to the calculation results, pristine graphene is limited to forming weak physical adsorption with SO2 and vacancy defects can lead to only limited improvement of adsorption capacity. In addition, as a suitable dopant, Ti is effective in improving the adsorption energy and charge density of the adsorption system, and in promoting the formation of chemisorption. Besides, after the absorption of SO2 molecules, an impurity band appears in the band structure of Ti-doped graphene, which significantly increases the density of states near the Fermi level. In case of vacancy defects in the Ti-doped graphene, the adsorption capacity will decline. Therefore, Ti-doped graphene exhibits the highest SO2 molecules adsorption capacity among the materials calculated in this paper.