Tunning Hydrogen Storage Properties of Carbon Ene–Yne Nanosheets through Selected Foreign Metal Functionalization

Abstract

In this study, we have employed density functional theory with a range of van der Waals corrections to study geometries, electronic structures, and hydrogen (H 2 ) storage properties of carbon ene−yne (CEY) decorated with selected alkali (Na, K) and alkaline-earth metals (Mg, Ca). We found that all metals, except Mg, bind strongly by donating a major portion of their valence electrons to the CEY monolayers. Thermal stabilities of representative systems, Ca-decorated CEY monolayers, have been confirmed through ab initio molecular dynamics simulations (AIMD). We showed that each metal cation adsorbs multiple H 2 with binding energies (E bind ) considerably stronger than on pristine CEY. Among various metal dopants, Ca stands out with the adsorption of five H 2 per each Ca having E bind values within the desirable range for effective adsorption/desorption process. The resulting gravimetric density for CEY@Ca has been found around 6.0 wt % (DFT-D3) and 8.0 wt % (LDA), surpassing the U.S. Department of Energy's 2025 goal of 5.5 wt %. The estimated H 2 desorption temperature in CEY@Ca exceeds substantially the boiling point of liquid nitrogen, which confirms its potential as a practical H 2 storage medium. We have also employed thermodynamic analysis to explore the H 2 adsorption/desorption mechanism at varied conditions of temperature and pressure for real-world applications.

Tuning Hydrogen Storage Properties of Li- and Na-Decorated 3D Carbon-Honeycomb through a Physisorption Process

“…As shown in Figure , the minimum, average, and maximum T D values at standard atmospheric pressure are 114, 160, and 287 K for the Li@C-honeycomb (112, 142, and 281 K for the Na@C-honeycomb), respectively, which highly exceed the boiling point of liquid nitrogen (77 K). Meanwhile, these values of average desorption temperatures are comparable to, or even higher than, those of some previously explored lithium-/sodium-decorated carbon nanostructures, such as Li@BPNTs (104 K), Na@carbon ene-yne (112 K), Li/Na@t-graphene monolayer (142/127 K), and Li@carbyne monolayer (149 K) . It is also observed that if we increase the equilibrium pressure, the value of the desorption temperature increases.…”

Bilayer Heterostructure of Boron Nitride and Graphene for Hydrogen Storage: A First-Principles Study

“…Grimme's semi-empirical D2 and D3 dispersion correction are proven to be better choice for weakly interacting hydrogen-bonded systems. 11,92 The single hydrogen molecule binding energy on h-BN/Gr is higher in comparison to many available results in the literature and also compared to its pristine counterparts. 25,34,35,93,94 We further tested the binding energy of a single hydrogen molecule on two more bilayer structures with AA type (where hexagon of graphene is symmetric with hexagon of boron nitride) and AB-Boron type (where boron atom is at the center of graphene hexagon) [refer to Figure S8 in Supporting Information] stacking orientation of h-BN/Gr.…”

“…Hydrogen molecules binding capability on the h-BN/Gr is tested first by calculating the binding energy of H 2 molecules using the following equation ,,, E normalB normalE = E normalT normalo normalt normala normall − ( E h − B N / G r + n E H 2 ) A single hydrogen molecule prefers a parallel orientation at the hexagonal site of the BN-ring with a binding energy of −1.37(−1.48) eV calculated by employing the DFT-D2(D3) Grimme’s dispersion method. Grimme’s semi-empirical D2 and D3 dispersion correction are proven to be better choice for weakly interacting hydrogen-bonded systems. , The single hydrogen molecule binding energy on h-BN/Gr is higher in comparison to many available results in the literature and also compared to its pristine counterparts. ,,,, We further tested the binding energy of a single hydrogen molecule on two more bilayer structures with AA type (where hexagon of graphene is symmetric with hexagon of boron nitride) and AB-Boron type (where boron atom is at the center of graphene hexagon) [refer to Figure S8 in Supporting Information] stacking orientation of h-BN/Gr. The single hydrogen molecule adsorption energies on these AA-type and AB-type configuration are −0.94(−0.97) and −1.01(−1.03) eV, respectively.…”

In-Plane Hybrid Structure of h-BN and Graphene for Hydrogen Storage Application: A First-Principles Density Functional Theory Study

“…To evaluate the hydrogen storage properties, the binding energy, average adsorption energy, gravimetric density, and desorption temperature are calculated. The quantitative value of binding energy ( E BE ) is obtained using eq , ,− E normalB normalE = E n H 2 + B N − G r − ( E normalB normalN − normalG normalr + n E H 2 ) …”

“…The average adsorption energy ( E ads eV/H 2 ) of adsorbed H 2 molecules are computed by using eq , ,− E normala normald normals .25em ( normale normalV / normalH 2 ) = E n H 2 + B N − G r − ( E normalB normalN − normalG normalr + n E H 2 ) n where E BN–Gr , E H2 , and E n H 2 +BN–Gr are the respective total energies of h-BN/Gr hybrid-structure, an isolated H 2 molecule, H 2 molecules adsorbed in the hybrid structure in their lowest-energy configuration and n is the number of H 2 molecules adsorbed. It is an important criterion to distinguish the mode of adsorption (physical or chemical) of hydrogen molecules on storage materials.…”