DFT-D3 and AIMD investigation of hydrogen storage in the Li-decorated carbon-doped BN analogue of 8-16-4 graphyne

Abstract

Density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations were performed to investigate hydrogen storage in a carbon-doped boron nitride (BN) lattice derived from the 8-16-4 graphyne structure, decorated with lithium atoms. Carbon incorporation into the SBNyne lattice significantly increases the binding affinity of Li adatoms and prevents Li clustering. As a result, the newly developed material 2Li@C-SBNyne contains two strongly bound Li adatoms per unit cell that can adsorb hydrogen molecules efficiently. Each Li atom can coordinate up to four H₂ molecules, giving a maximum of eight H₂ molecules per C-SBNyne unit cell, with an average adsorption energy of approximately E_ad = −0.163 per H₂ and a hydrogen storage capacity of 7.12%. The adsorption energy lies within the optimal range for reversible storage, and the gravimetric capacity exceeds the U.S. Department of Energy (DOE) 2025 onboard hydrogen storage gravimetric target of 5.5 wt%. Thermodynamic analysis predicts a desorption temperature of approximately 209 K. AIMD runs of 8 ps at 209 K and 300 K show strong adhesion of the Li adatoms to the C-SBNyne lattice and preservation of the molecular integrity of the adsorbed H₂, indicating good thermal stability.