Reversible hydrogen storage tendency of light-metal (Li/Na/K) decorated carbon nitride (C9N4) monolayer

Abstract

<p>The emergence of hydrogen (H₂) as a future carrier of energy and the issue related to its storage leads to the exploration of two-dimensional materials, which have the potential to be explored as H₂ storage materials. In this regard, potential of alkali metals (Li/Na/K) decorated two-dimensional carbon-nitride (C₉N₄) monolayer is studied for H₂ storage by performing first-principles density functional theory (DFT) computations. Metal dopants, Li, Na, and K show strong binding interactions with the C₉N₄ due to the transfer of charges from the formers to the later. In addition to strong bindings with C₉N₄ high diffusion barriers further nullify the cluster formation among metal dopants. The effect of temperature on the stability of alkali metal decorated C₉N₄ is studied in terms of ab-initio molecular dynamics (AIMD) simulations. The effect of metal decoration on electronic as well as magnetic properties of C₉N₄ are studied in terms of partial density of states (PDOS) plots. We find that each Li of Li-doped C₉N₄ (Li@C₉N₄) can stably binds six H₂ molecules without disintegration and results in the average adsorption energy of −0.20 eV, leading to a notably high H₂ storage capability of 11.9 wt%. Similarly, the storage capacities and average H₂ adsorption energies in the case of Na@C₉N₄ and K@C₉N₄ complexes fulfil the US Department of Energy (DOE) criteria. The electronic, AIMD, and thermodynamics analysis in this study provide an insight into that alkali metal decorated C₉N₄ as reversible H₂ storage material.</p>