Lithium doped g-C₆N₇ monolayer as a reversible hydrogen storage media

Two-dimensional materials have a larger specific surface area and more active sites and are widely used in the design of hydrogen storage media. In this article, the hydrogen-storage properties of Li-decorated g-C6N7 monolayer are investigated by the density functional theory. It is found that the g-C6N7 monolayer possesses the thermodynamic and dynamic stability and the Li-decorated g-C6N7 monolayer is also thermodynamically stable under 500 K. The calculation of the electronic structure reveals that covalent bonds are formed between C and N atoms and there are not only orbital interactions but also ionic bonds between Li atoms and the g-C6N7 sheet. The hydrogen storage performance for the Li-doped g-C6N7 sheet indicates that the storage capacity of hydrogen reaches 11.94 wt%, and the average adsorption energy of H-2 molecule is -0.145 similar to -0.196 eV, which is attributed to electrostatic attraction, weak orbital interactions and van der Waals interaction. The value of the adsorption energy of H-2 molecule and the capacity of hydrogen storage reveal that the g-C6N7 monolayer modified by Li atoms can be used as a reversible and promising hydrogen storage medium.