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, C2N, 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. (c) 2019 Published by Elsevier Ltd.