DFT-D3 and AIMD Investigation of Hydrogen Storage in Li-Decorated Carbon-Doped BN Analogue of 8-16-4 Graphyne

Abstract

Density functional theory (DFT) and ab initio molecular dynamics simulations were performed to investigate hydrogen storage in a carbon-doped boron nitride (BN) lattice based on the 8-16-4 graphyne structure, which has been decorated with lithium atoms. The addition of carbon to the SBNyne lattice increases the binding affinity of lithium atoms significantly and precludes their clustering. Therefore, the newly developed material 2Li@C-SBNyne consists of two strongly bonded lithium adatoms to the C-SBNyne monolayer that can adsorb hydrogen molecules efficiently. Each of the lithium atoms in the 2Li@C-SBNyne structure can surround itself with four hydrogen molecules, leading to a maximum of 8 hydrogen molecules per C-SBNynene unit cell and an average adsorption energy of approximately E ad = -0.163 eV per hydrogen molecule, yielding a hydrogen storage capacity of 7.12 % . The hydrogen adsorption energy lies within the optimal hydrogen storage range established by the Department of Energy (DOE), and the hydrogen storage capacity exceeds the Department's target. The thermodynamic analysis predicts the desorption temperature for the C-SBNyne to be approximately 209K. The dynamic response of the lithium adatoms was examined by AIMD at both 209K and 300K for 2 ps duration (with a 0.5 fs time step) and showed strong adhesion of the lithium adatoms to the C-SBNyne structure and intactness of the H 2 molecules, indicating good thermal stability.