Density Functional Theory Study of Superalkali NLi₄-Decorated Graphdiyne Nanosheets as Hydrogen Storage Materials

The properties and mechanism of adsorption of hydrogen molecules on NLi 4 -decorated graphdiyne nanosheets (NLi 4 -GDY) were investigated based on the density functional theory. Accordingly, the 76 hydrogen storage configurations of NLi 4 -SGDY, NLi 4 -GDY-A, and NLi 4 -SGDY-A were constructed by nonmetallic B/N substitution and A (A = B, N, Si, P) adsorption. The electronic structure of each configuration and the structure with the desired high hydrogen storage capacity were explored. The results showed that the charge on the lithium atom in the NLi 4 -GDY structure was transferred to the pristine GDY, thus forming a partial electron field around each lithium atom, which subsequently led to the polarized adsorption of the hydrogen molecule. Through B/N substitution and A adsorption, we have modulated the degree of charge transfer in Li atoms across different configurations, thereby manipulating the strength of partial electric fields and resulting in varying hydrogen storage capacities for NLi 4 -SGDY, NLi 4 -GDY-A, and NLi 4 -SGDY-A configurations. According to DFT calculations, the optimal hydrogen storage structures for NLi 4 -GDY, NLi 4 -SGDY, NLi 4 -GDY-A, and NLi 4 -SGDY-A were 6H 2 -2NLi 4 -GDY, 14H 2 -2NLi 4 -N11′, 14H 2 -2NLi 4 -GDY-Si, and 18H 2 -2NLi 4 -N1-P, respectively, with gravimetric densities of 3.85, 8.09, 7.29, and 8.91 wt %, respectively. Considering the exceptional hydrogen storage properties of the aforementioned configurations, we propose that NLi 4 -decorated GDY with B/N substitution and A adsorption offers a promising avenue for discovering novel hydrogen storage materials.