Enhancement in hydrogen storage capacities of light metal functionalized Boron–Graphdiyne nanosheets

The recent experimental synthesis of the two-dimensional (2D) boron-graphdiyne (BGDY) nanosheet has motivated us to investigate its structural, electronic, and energy storage properties. BGDY is a particularly attractive candidate for this purpose due to uniformly distributed pores which can bind the light-metal atoms. Our DFT calculations reveal that BGDY can accommodate multiple light-metal dopants (Li, Na, K, Ca) with significantly high binding energies. The stabilities of metal functionalized BGDY monolayers have been confirmed through ab initio molecular dynamics simulations. Furthermore, significant charge-transfer between the dopants and BGDY sheet renders the metal with a substantial positive charge, which is a prerequisite for adsorbing hydrogen (H ₂ ) molecules with appropriate binding energies. This results in exceptionally high H ₂ storage capacities of 14.29, 11.11, 9.10 and 8.99 wt% for the Li, Na, K and Ca dopants, respectively. These H ₂ storage capacities are much higher than many 2D materials such as graphene, graphane, graphdiyne, graphyne, C ₂ N, silicene, and phosphorene. Average H ₂ adsorption energies for all the studied systems fall within an ideal window of 0.17–0.40 eV/H ₂ . We have also performed thermodynamic analysis to study the adsorption/desorption behavior of H ₂ , which confirms that desorption of the H ₂ molecules occurs at practical conditions of pressure and temperature.