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.

Atmospheric pollutants pose a high risk to human health, and therefore it is necessary to capture and preferably remove them from ambient air. In this work, we investigate the intermolecular interaction between the pollutants such as CO, CO 2 , H 2 S, NH 3 , NO, NO 2 , and SO 2 gases with the Zn 24 and Zn 12 O 12 atomic clusters, using the density functional theory (DFT) at the meta-hybrid functional TPSSh and LANl2Dz basis set. The adsorption energy of these gas molecules on the outer surfaces of both types of clusters has been calculated and found to have a negative value, indicating a strong molecular-cluster interaction. The largest adsorption energy has been observed between SO 2 and the Zn 24 cluster. In general, the Zn 24 cluster appears to be more effective for adsorbing SO 2 , NO 2 , and NO than Zn 12 O 12 , whereas the latter is preferable for the adsorption of CO, CO 2 , H 2 S, and NH 3 . Frontier molecular orbital (FMO) analysis showed that Zn 24 exhibits higher stability upon adsorption of NH 3 , NO, NO 2 , and SO 2 , with the adsorption energy falling within the chemisorption range. The Zn 12 O 12 cluster shows a characteristic decrease in band gap upon adsorption of CO, H 2 S, NO, and NO 2 , suggesting an increase in electrical conductivity. Natural bond orbital (NBO) analysis also suggests the presence of strong intermolecular interactions between atomic clusters and the gases. This interaction was recognized to be strong and noncovalent, as determined by noncovalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses. Overall, our results suggest that both Zn 24 and Zn 12 O 12 clusters are good candidate species for promoting adsorption and, thus, can be employed in different materials and/or systems for enhancing interaction with CO, H 2 S, NO, or NO 2 .

No abstract