Abstract:
Exploring efficient storage mediums is the key challenge to accomplish a sustainable
hydrogen economy. Material-based hydrogen (H2) storage is safe, economically viable and
possesses high gravimetric density. Here, we have designed a novel H2 storage architecture
by decorating graphene-like haeckelite (r57) sheets with the super-alkali (NLi4) clusters,
which bonded strongly with the r57. We have performed van der Waals corrected density
functional theory (DFT) calculations to study the structural, electronic, energetic, charge transfer, and H2 storage properties of one-sided (r57-NLi4) and two-sided (r57-2NLi4)
coverage of r57 sheets. Exceptionally high H2 storage capacities of 10.74%, and 17.01% have
been achieved for r57-NLi4, and r57-2NLi4 systems, respectively that comfortably surpass
the U.S. Department of Energy's (DOE) targets. Under maximum hydrogenation, the
average H2 adsorption energies have been found as 0.32 eV/H2, which is ideal for
reversible H2 storage applications. We have further studied the effects of mechanical strain
to explore the H2 desorption mechanism. Statistical thermodynamic analysis has been
employed to study the H2 storage mechanism at varied conditions of pressures and temperatures. Our findings validate the potential of r57-xNLi4 as efficient H2 storage materials.
