Density functional theory investigation of hydrogen storage on superalkali OLi3 decorated graphene

Abstract

Design and synthesis of high performance hydrogen storage material is a critical issue towards achieving the goals of carbon peaking and carbon neutrality. Utilizing on density functional theory (DFT) investigation, this paper comprehensively examines H₂ storage properties on superalkali OLi₃ cluster decorated graphene and the results expose that the OLi₃ cluster can firmly bind on graphene owing to the highest binding energy of −2.87 eV. Moreover, double sides of OLi₃-decorated graphene can hold the maximum number of 18 H₂ molecules, achieving an ideal H₂ adsorption energy of −0.201 eV/H₂ as well as the satisfied hydrogen storage capacity of 7.29 wt%, which exceeds the specified target of 5.5 wt% by U.S. Department of Energy (DOE) for 2025 year. The obtained partial density of states (PDOS), charge density difference (CDD) and the isosurface of electrostatic potential (ESP) clearly reflect the H₂ adsorption mechanisms, which mainly consists of orbital hybridization and polarization effect. In addition, ab initio molecular dynamics (AIMD) simulations guarantee an excellent thermodynamic stability for 18H₂/2OLi₃/G system at 300 K through 3 ps simulations and the H₂ molecules can be quickly released under higher temperature in basis of the recovery times (τ). Furthermore, the N-P-T diagram shows the adsorption conditions of H₂ molecules require low temperature and high pressure while the conditions of desorption are just the opposite. Our theoretical predictions can pave the way for the experimental synthesis of high capacity hydrogen storage materials.