Enhanced hydrogen storage properties under external electric fields of N-doped graphene with Li decoration

Abstract

In this article, the imposition of an external electric field is proposed as an effective means to improve the hydrogen storage properties of a promising medium. To demonstrate the feasibility of this concept, the geometric stability and hydrogen capacity of Li functionalized N-doped graphene were investigated in the presence of an electric field using density functional theory (DFT) calculations. For Li decorated pristine and graphitic structures, the binding energy of the Li atom on the surface sheets exceeded the cohesive energy of the Li metal bulk under a positive electric field. From these results, Li adatom dispersion with atomic accuracy is expected for these two unstable structures. Furthermore, the hydrogen adsorption behavior of the pyridinic and pyrrolic structures was changed by the applied electric field in the range of 0.14-0.27 eV. It is therefore anticipated that the adsorption and desorption processes can be easily controlled using suitable field strength and direction.