Ca-decorated novel boron sheet: A potential hydrogen storage medium

•Ca atoms are bonded to a novel B sheet strongly without clustering.•Six H2 molecules can be captured by every Ca atom in the B sheet.•Hydrogen density of 12.68 wt.% is reached when Ca are adsorbed on both sides of the B sheet.•H2 still be adsorbed by the Ca-decorated B sheet at room temperature and mild pressure.

We studied hydrogen storage properties of Ca-decorated a novel boron sheet through first-principles calculations. It was found that up to six H2 molecules can be captured by a Ca atom at 0 K with an average binding energy in a better range of −0.20 to −0.32 eV/H2. The gravimetric hydrogen density of 12.68 wt.% is reached when Ca is adsorbed on both sides of the boron sheet. The mechanism for binding the attached H2 molecules comes from not only the polarization mechanism but also the orbital hybridization. The effect of temperature and pressure on hydrogen storage performance of the Ca-decorated boron sheet was also evaluated. At room temperature, all the hydrogen adsorbed structures are stable at mild pressure. Our results indicate that Ca-decorated boron sheet is a potential hydrogen storage medium for on-board vehicle application.