Computational exploration of high-capacity hydrogen storage in alkali metal-decorated MgB2 material

Abstract

In this study, a novel substrate complex is developed by integrating alkali metals such as Li/Na/K onto magnesium diboride (MgB2). The research involves comprehensive density functional theory (DFT) to analyze the complex optimized structures, thermodynamic characteristics, and H2 storage capabilities. The results underscore a subtle charge transfer from Li/Na/K to the pristine MgB2 monolayer, augmenting its electropositive characteristics. This attribute proves particularly advantageous for H2 storage, as it enhances the electrostatic interactions between the complex and hydrogen (H2) molecules. The structure of Li/Na/K-decorated MgB2 with various numbers of attached H2 molecules is also explored. The maximum H2 adsorption is observed with nine H2 molecules for Li (n = 9H2) and eight H2 molecules for both Na and K (n = 8H2). The adsorption energies for these configurations fall within the range of −0.24 to −0.21 eV for Li, −0.22 to −0.20 eV for Na, and −0.25 to −0.20 eV for K. Notably, gravimetric capacities of 14.6 wt%, 23.37 wt%, and 18.94 wt% are attained for Li, Na, and K-decorated MgB2, respectively. These values demonstrate a significant surpassing of the U–S Department of Energy (DOE) target of 5.5 wt%. This groundbreaking material has the potential to play a crucial role in promoting efficient and sustainable solutions for H2 storage, meeting the increasing need for clean energy technologies.