Superalkali functionalized two-dimensional haeckelite monolayers: A novel hydrogen storage architecture

Abstract

<p>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.</p>