A DFT study on defects and N doping to enhance hydrogen storage in Mg-decorated graphene

Abstract

In this study, first-principles calculations were used to conduct in-depth studies on multiple key aspects of N-doped defective graphene modified with Mg atoms, including structure, electronic property, thermal stability, as well as hydrogen storage performance and mechanism. The research results show that after the introduction of Mg, N atoms and vacancy defects, pristine graphene transforms from semi-metallic property to metallic property. And the AIMD results indicate excellent thermodynamic stability of the substrate. It can adsorb up to seven H2 molecules, and the adsorption energy values is between −0.15 and −0.21 eV, which is in the stable energy range (-0.15 to −0.60 eV). The hydrogen storage mechanism is mainly attributed to the van der Waals force caused by the polarization of H2 molecules and orbital hybridization between H atoms and the substrate. The calculation of the desorption temperature shows that this substrate can become a potential candidate for reversible hydrogen storage materials at temperatures above 206 K. Compared with graphene decorated with Mg atoms, the introduction of N atoms and vacancy defects significantly improved the hydrogen storage performance.