Exploring the ultra-high hydrogen storage capacity of Li-decorated h-B2S3 nanosheet: A DFT-D3 study

Surface functionalization of two-dimensional (2D) nanomaterials with metals can enhance their performance and energy storage capacities. Alkali-metal decorated hexagonal boron trisulfide (h-B2S3) nanosheets can be economical for energy storage applications. Here we performed dispersion-corrected density functional theory (DFT-D3) calculations to investigate the electronic and structural properties of pristine and Li-functionalized hB2S3 nanosheets. The thermodynamic feasibility and interatomic interactions were characterized based on the adsorption energies and atoms-in-molecules (AIM) analysis. The pristine h-B2S3 nanosheet showed weak interactions with hydrogen molecules whereas the Li-decorated nanosheet demonstrated greater affinity for hydrogen. Furthermore, the Li-based h-B2S3 nanosheet exhibits a large hydrogen gravimetric density of 6.35 wt% which is above the United States Department of Energy (US DOE) goal (5.50 wt%) by the end of the year 2025. Li-decorated h-B2S3 also demonstrates better stability for various temperatures, as predicted by ab initio molecular dynamics (AIMD) simulations. The desorption temperatures of hydrogen were calculated to assess the efficiency of the hydrogen uptake-release cycle. The obtained desorption temperature (209.84 K) at ambient conditions for the saturated Li-functionalized nanosheet suggests hydrogen storage well above its critical point, predicting safe and energy-efficient hydrogen storage in the functionalized nanosheets. Hence, Li-decorated hB2S3 nanosheets emerge as a potential 2D nanomaterial for high-capacity hydrogen storage systems.