Computational Evaluation of Li-doped g-C2N Monolayer as Advanced Hydrogen Storage Media

The emerging 2D g-C2N obtained increasingly more popularity in functional materials design, and its natural porosity can easily accommodate metal atoms, making itself more suitable for energy gases storage. In this study, we employed DFT computational studies to systematically solve the electronic structure of Li-doped g-C2N monolayer, and evaluate its performance in hydrogen storage. In our calculations, we found that each pore of g-C2N can adsorb at most three Li atoms that bind with pyridinic N atoms. We also noticed that considerable amount of charges were transferred from the adsorbed Li to the pristine materials, potentially enhancing its overall conductivity. The change of electronic structure also leads to its improved performance in H2 adsorption, due to the fact that the electrostatic interactions between the adsorbed H2 and Li can be largely enhanced. The optimised configurations of the Li-doped g-C2N with multiple adsorbed H2 molecules were presented, and the fundamental mechanisms of adsorption were also investigated in details. The highest storage capacity of hydrogen by Li-doped g-C2N can reach to 7.8 wt%, much higher than the target value of 5.5 wt %, defined by the U.S department of energy (DOE). Moreover, except Li, we also found that the nitrogen atoms or the N-C bonds can also serve as active adsorption sites. The computational explorations conducted in this study actually indicates a promising prospect of alkali metals decorated 2D materials in the area of hydrogen storage; and we believe the performance of these kinds of novel materials can be further enhanced via more decent modifications.