Distribution of oxygen-containing functional groups on defective graphene: properties engineering and Li adsorption

In this study, the distribution of oxygen-containing functional groups on graphene with vacancies and topological defects was systematically investigated using advanced computational methods and the structure models for multi-defect graphene oxides (GOs) were proposed. All potential adsorption sites were considered through an automated structure generation program to identify energetically favorable structures. Unlike the pristine graphene surface where oxygen-containing functional groups always aggregate with each other, we observed a tendency for them to preferentially adsorb near defects. Furthermore, they may also be distributed on the same side or both sides of the defective graphene. These multi-defect GOs can exhibit either metallic or semiconducting properties. Notably, upon adsorbing the same oxygen-containing functional groups onto the surface of defective graphene, their electronic characteristics become homogeneous. The coexistence of vacancy/topological defects and oxygen-containing functional groups within the graphene lattice introduces intriguing mechanical anisotropic properties to graphene, including the uncommon negative Poisson's ratio. Additionally, these materials exhibit anisotropic optical behavior, displaying heightened absorption within the infrared and visible regions compared to pristine graphene. Finally, it is found that Li atoms are adsorbed stably on the surfaces of multi-defect GOs via the formation of LiO/LiOH clusters. The research findings presented in this paper, encompassing the development of structural models for multi-defect GOs, could provide crucial insights into the properties and potential applications of graphene oxides.