Balancing capacity, stability, and functionality in MgB2H8: A DFT-based framework for solid-state hydrogen storage

The development of solid-state hydrogen storage materials requires balancing high storage capacity with favorable thermodynamics and rapid hydrogen transport. Complex borohydrides offer exceptional hydrogen densities but often suffer from high desorption temperatures and slow kinetics. Here, we investigate magnesium borohydride MgB 2 H 8 as a potential hydrogen storage material using density functional theory, climbing-image nudged elastic band calculations, and ab initio molecular dynamics simulations. MgB 2 H 8 exhibits a gravimetric hydrogen capacity of 11.1 wt% and a volumetric density of 45 g L −1 , exceeding U.S. Department of Energy 2025 targets. A negative formation energy (−1.80 eV per formula unit) and AIMD simulations confirm thermodynamic and dynamic stability. The calculated hydrogen desorption enthalpy (∼42 kJ mol −1 H 2 ) is significantly lower than that of MgH 2 , while diffusion barriers of 0.40–0.80 eV indicate moderate hydrogen mobility. Bonding analysis reveals covalent B–H interactions stabilized by ionic Mg coordination. These results identify MgB 2 H 8 as a promising candidate for next-generation solid-state hydrogen storage.