DFT study of the hydrogen adsorption and storage on Ni4 cluster embedded in multivacancy graphene

Hydrogen adsorption stability, geometry, electronic structure and mechanism has been investigated on Ni-4 cluster embedded in graphene with three, four and six vacancies by density functional theory (DFT) calculations. An energetic analysis of hydrogen adsorption by addition of one to four H-2 molecules was performed for each system in order to determine their hydrogen storage capacity. Dispersion force contribution to the adsorption energy is quantitative evaluated to know whether H-2 molecules adsorption behavior is dominated by chemical or van der Waals interactions. A further analysis of this type of interactions is also addressed by total and partial density of states. Bonding and charge transfer characteristics for the different steps involved in the adsorption mechanism are also included. Special attention is given to the effects caused by this new Ni/graphene interface to the hydrogen adsorption behavior. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.