Toward Site-Specific Interactions of nH2 (n=1-4) with Ga12As12 Nanostructured for Hydrogen Storage Applications

While hydrogen combustion generates a lot of energy and can be done in a variety of ways, the primary challenge in utilizing hydrogen energy is obtaining an efficient hydrogen storage material. Herein, the potential of Ga12As12 as a hydrogen adsorbent and storage material was investigated within the framework of density functional theory (GGA-DFT) computations at the B3LYP-GD3BJ/def2tzvp level of theory. The study was systematically conducted by increasing the number of molecular hydrogen adsorptions (n = 1-4) at Ga-and As-sites of the Ga12As12 adsorbent material. Results showed that adsorption on the As site is preferred as the hydrogen binding on this site is closer to the DoE requirement. Via DFT-GGA with the incorporation of D3 dispersion, we demonstrated that the Ga12As12 nanocluster can store up to four molecular hydrogens with a calculated gravimetric wt % of 5.71%, closer to the 6.5 wt % proposed by the DoE. Average binding energies for both As and Ga adsorption sites were observed to be -0.49 and -0.84 eV, respectively, which is within the range of H2 adsorption energy according to DoE. The electronic properties, thermodynamics, and the density of state disclosed a linear relationship with the increase in H2 adsorption. This trend is also seen in the adsorption energy, which shows a higher adsorption range as the number of hydrogen molecules on the Ga12As12 nanocage increases. Ab initio molecular dynamics simulations divulged that the studied system is considerably stable both at room temperature and at extreme temperatures. Based on the utilization of GGA exchange correlations, confirmation of stability via ab initio MD simulations, high desorption temperature (1454 K), and the computed gravimetric wt % (5.71), which is close to the DoE standard (6.5%), we strongly believe that proper surface engineering of the studied Ga12As12 nanocluster could further improve the overall properties and suitability toward hydrogen storage applications.

Automated summary

The primary challenge in utilizing hydrogen energy is obtaining an efficient hydrogen storage material. In this study, Ga12As12 was investigated as a hydrogen adsorbent and storage material. The results showed that Ga12As12 can store up to four molecular hydrogens with an adsorption energy within the range of H2 adsorption energy according to the DoE. The stability and suitability of Ga12As12 for hydrogen storage applications were confirmed through ab initio molecular dynamics simulations, high desorption temperature, and gravimetric wt % close to the DoE standard.