First-principles investigation of hydrogen storage capacity of Y-decorated porous graphene

Based on first-principles method, the electron structure of porous graphene (PG) and adsorption ability of H2 molecular on Y-decorated porous graphene are investigated using CASTEP code. It is found that the bridge of C-C bond which connects two C hexagons is favorable site for a Y atom adsorbed on the single side of PG, and six H2 molecules can be absorbed around a Y atom with average adsorption energy of −0.297 eV/H2 computed by GGA-PBE functional. Though two Y atoms can be stably adsorbed on the same side of one unit cell of PG, there isn't sufficient space for H2 absorbing around each Y atom. To improve capability of hydrogen storage, the unit cell of PG with single side should only contain one Y atom. For the case of double side of porous graphene, two Y atoms are preferably located above the center of the different C hexagon. Fourteen H2 molecules can be absorbed on both sides of PG, and the gravimetric hydrogen storage capacity is 7.87 wt.% with the average adsorption energy of −0.23 eV/H2.