Enhanced hydrogen storage of alkaline earth metal-decorated B_n (n = 3-14) nanoclusters: a DFT study

Context: Boron-based nanostructures hold significant promise for revolutionizing hydrogen storage technologies due to their exceptional properties and potential in efficiently accommodating and interacting with hydrogen molecules. In this paper, boron-based B_n (n = 3-14) nanoclusters decorated with alkaline earth metals (AEM = Ca and Be) were investigated for hydrogen storage applications based on density function theory (DFT) calculations. To evaluate H₂ adsorption capability, the adsorption energies, frontier molecular orbitals (FMOs), natural bond orbital (NBO), and quantum theory of atoms in molecule (QTAIM) analysis are performed. The primary aim of this research work is to achieve targeted value of 5.5 wt% set by the US Department of Energy (DOE) for the year 2025. The results revealed that B₅Ca₂, B₆Ca₂, and B₁₀Ca₂ structures have the ability to hold up to 12H₂ molecules with gravimetric capacities of 15.20, 14.21, and 8.60 wt%, respectively, when compared to other boron structures decorated with calcium. Similarly, for Be-decorated structure, B₃Be₂ structure can accommodate 3H₂ molecules with gravimetric capacity of 10.59 wt%. The result of this study indicates that AEM-decorated B_n nanoclusters hold great promise as potential materials for hydrogen storage.

Methods: Density functional theory (DFT) approach at ωB97XD/6-311++G(d,p) level of theory is employed to investigate the possibility of storing H₂ molecules on alkaline earth metal (AEM = Ca and Be)-decorated B_n (n = 3-14) nanoclusters. All DFT computations were performed using Gaussian 09 software. To calculate frontier molecular orbitals (FMOs) and quantum theory of atoms in molecule (QTAIM) analysis, we have used GaussView and Multiwfn software, respectively.