Hydrogen Storage by Polylithiated Molecules and Nanostructures

TL;DR

This study explores polylithiated molecules and their nanostructures as promising hydrogen storage materials, demonstrating high gravimetric densities and stable attachment to graphene, which could enhance hydrogen storage technologies.

Contribution

It introduces polylithiated molecules and their graphene-based nanostructures as novel hydrogen storage materials with high capacity and favorable kinetics, based on first-principles calculations.

Findings

$ ext{ClLi}_4$ and $ ext{Li}_2 ext{O}$ bind 12 and 10 H$_2$ molecules respectively

Hydrogen gravimetric densities reach 37.8% and 40.3% by weight

Graphene doping enhances molecule stability and storage capacity

Abstract

We study polylithiated molecules as building blocks for hydrogen storage materials, using first-principles calculations. $\clifour$ and $\olitwo$ bind 12 and 10 hydrogen molecules, respectively, with an average binding energy of 0.10 and 0.13 eV, leading to gravimetric densities of 37.8 and 40.3 weight % H. Bonding between Li and C or O is strongly polar and $\hyd$ molecules attach to the partially charged Li atoms without dissociating, which is favorable for (de)hydrogenation kinetics. CLi$_n$ and OLi$_m$ molecules can be chemically bonded to graphene sheets to hinder the aggregation of such molecules. In particular B or Be doped graphene strongly bind the molecules without seriously affecting the hydrogen binding energy. It still leads to a hydrogen storage capacity in the range 5-8.5 wt % H.