Supported Metal Nanohydrides for Hydrogen Storage

Adsorption of hydrogen on graphdiyne (GDY) and boron-graphdiyne (BGDY) doped with palladium clusters has been investigated by performing density functional calculations. Pd6 fits well on the large holes of those porous layers, preserving its octahedral structure in GDY and changing it to a capped trigonal bipyramid structure in BGDY. Pd6GDY adsorbs up to five H2 molecules with sizable adsorption energies, two dissociated and three nondissociated. The dissociation barrier of H2 on the Pd6GDY cluster is 0.58 eV. Pd6BGDY can adsorb up to six molecules, three dissociated and three nondissociated, and the dissociation barrier of H2 on Pd6BGDY is 0.23 eV. In both cases, the dissociation barriers are substantially smaller than the corresponding dissociation barriers on undoped GDY and BGDY. The Pd clusters saturated with hydrogen can be viewed as nanohydrides. Spilling of the adsorbed hydrogen atoms toward the GDY and BGDY substrates is hindered by large activation barriers. We then propose using BGDY and GDY layers as support platforms for metal nanohydrides. The amount of stored hydrogen using Pd as the dopant is below the target of 6% of hydrogen in weight, but replacing Pd by a lighter metal with similar or higher affinity for hydrogen would substantially enhance the storage.

Automated summary

This study investigates the adsorption of hydrogen on graphdiyne (GDY) and boron-graphdiyne (BGDY) doped with palladium clusters using density functional calculations. The results show that Pd6 fits well on the large holes of GDY and changes its structure to a capped trigonal bipyramid structure in BGDY. Pd6GDY can adsorb up to five H2 molecules while Pd6BGDY can adsorb up to six molecules, with both having smaller dissociation barriers compared to undoped GDY and BGDY.