First-principles study of sodium adsorption and diffusion on vacancies, N, S, and NS-codoped graphene

Abstract

The graphene and its derivative are potential candidates as an electrode for the Na ion storage device. In practical applications, the effects of the heteroatoms doping and vacancy defects in graphene are still poorly known. Here, the first principles calculations have been performed on the geometric structures and the Na atom adsorption behaviors of the vacancies, N, S, and NS codoped on the graphene. The formation energy could be reduced by introducing the N atom, therefore, increasing the generation chances. The results of the adsorption energy indicate that the vacancies, N, and NS codoped on the graphene are favorable for Na atom adsorption. The NS codoped on the divacancies graphene (NS-DV-G) has appropriate formation energy, large adsorption energy, and could adsorb ten Na atoms without forming the cluster. The DOS curves indicate the coexistence of ionic and covalent bonds between the Na-sp hybridization states and the substrates. The Na atom migration energy barrier of NS-DV-G is 1.26 eV, which is higher than that of pristine graphene, but smaller than that of the epoxide group on the graphene. Overall, these studies indicate that NS-DV-G could be a promising component of future electrode materials.