Ultrahigh reversible hydrogen storage in K and Ca decorated 4-6-8 biphenylene sheet

Abstract

By applying density functional theory (DFT) and ab-initio molecular dynamics (AIMD) simulations, we predict the ultrahigh hydrogen storage capacity of K and Ca decorated single-layer biphenylene sheet (BPS). We have kept various alkali and alkali earth metals, including Na, Be, Mg, K, Ca, at different sites of BPS and found that K and Ca atoms prefer to bind individually on the BPS instead of forming clusters. It was found that 2x2x1 supercell of biphenylene sheet can adsorb eight K, or eight Ca atoms, and each K or Ca atom can adsorb 5 H${}_2$, leading to 11.90 % or 11.63 % of hydrogen uptake, respectively, which is significantly higher than the DOE-US demands of 6.5 %. The average adsorption energy of H${}_2$ for K and Ca decorated BPS is -0.24 eV and -0.33 eV, respectively, in the suitable range for reversible H${}_2$ storage. Hydrogen molecules get polarized in the vicinity of ionized metal atoms hence get attached to the metal atoms through electrostatic and van der Waals interactions. We have estimated the desorption temperatures of H${}_2$ and found that the adsorbed H${}_2$ can be utilized for reversible use. We have found that a sufficient energy barrier of 2.52 eV exists for the movement of Ca atoms, calculated using the climbing-image nudged elastic band (CI-NEB) method. This energy barrier can prevent the clustering issue of Ca atoms. The solidity of K and Ca decorated BPS structures were investigated using AIMD simulations.

41 pages, 12 figures (included); Int. J. Hyd. Energy (in press)

References in corpus (6)

• Calcium-Decorated Graphene-Based Nanostructures for Hydrogen Storage
• Hydrogen storage of calcium atoms adsorbed on graphene: First-principles plane wave calculations
• Transition Metal-Ethylene Complexes as High-Capacity Hydrogen Storage Media
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• Scandium decorated C${}_{24}$ fullerene as high capacity reversible hydrogen storage material: Insights from density functional theory simulations
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• Influence of compressive strain on the hydrogen storage capabilities of graphene: A density functional theory study
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