Hydrogen storage properties of Li functionalized B2S honeycomb monolayers are studied using density functional theory calculations. The binding of H-2 molecules to the clean B2S sheet proceeds through physisorption. Dispersed Li atoms on the monolayer surface increase both the hydrogen binding energies and the hydrogen storage capacities significantly. Additionally, ab initio molecular dynamics calculations show that there is no kinetic barrier during H-2 desorption from lithiated B2S. Among the studied B8S4Lix (x = 1, 2, 4, and 12) compounds, the B8S4Li4 is found to be the most promising candidate for hydrogen storage purposes; with a 9.1 wt% H-2 content and 0.14 eV/H-2 average hydrogen binding energy. Furthermore, a detailed analysis of the electronic properties of the B8S4Li4 compound before and after H-2 molecule adsorption confirms that the interactions between Li and H-2 molecules are of electrostatic nature. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.