Calcium-decorated C4B32 heteroborospherene as a promising lightweight platform for potentially reversible hydrogen storage: A DFT study

The C 4 B 32 heteroborospherene has attracted significant interest as a potential lightweight platform for clean energy storage. In this study, the hydrogen adsorption characteristics of pristine and Ca-decorated C 4 B 32 are systematically investigated using density functional theory (DFT) calculations. The computational results indicate that pristine C 4 B 32 exhibits weak interactions with H 2 , showing positive adsorption energies at the carbon sites. In contrast, decoration with calcium atoms enhances the adsorption performance. Up to seven H 2 molecules can be accommodated on each of the four decorated Ca atoms, yielding a Ca 4 @C 4 B 32 -(H 2 ) 28 complex with a calculated gravimetric density of 9.24 wt%. The calculated average adsorption energy is −0.22 eV per H 2 , falling within the commonly reported range for reversible molecular hydrogen adsorption. Furthermore, Quantum Theory of Atoms in Molecules (QTAIM) and Nuclear Magnetic Resonance (NMR) analyses characterize the noncovalent nature of the Ca-H 2 interactions and clarify the electronic properties of the cluster. These findings suggest that Ca-decorated C 4 B 32 may serve as a useful model for the design of boron-based nanomaterials for hydrogen storage applications.