Improvement of the hydrogen storage performance of t-graphene-like two-dimensional boron nitride upon selected lithium decoration

Abstract

Lithium decoration enhances the hydrogen storage capacities, reversibility and diffusion kinetics of t-boron nitride monolayer.

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

“…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 average adsorption energy [ E ads (eV/H 2 )] are computed using the following equation: ,,, E normala normald normals = E normalT normalo normalt normala normall − ( E h − B N / G r + n E H 2 ) n where E Total is the total energy of the complex (h-BN/Gr+H2), E h–BN/Gr is the total energy of the h-BN/Gr heterostructure, n is the number of H 2 molecules, and E H 2 refer to the total energy of H 2 molecule. The hydrogen molecules are gradually increased on the hexagonal site of the cavity up to the maximum available adsorption sites, keeping in mind the average adsorption energy lying in the desirable range of −0.15 – −0.60 eV/H 2 . ,, In the case of 4H 2 molecules, adsorption energy per H 2 is −0.47 eV. Similarly, when the hydrogen molecules are increased to 8H 2 , the adsorption energy per H 2 reduces to 0.39 eV.…”

“…The result of the Mulliken charge analysis is listed in Table . Along with the enhanced orbital interactions, increased charge transfer can also be the reason for an improved adsorption energy per H 2 .The desorption temperature for 4–24H 2 molecules from the h-BN/Gr heterostructure are calculated using the Van’t Hoff equation ,,, T normalD ( K ) = false| E normala normald normals false| K normalB true( normalΔ S R − ln nobreak0em.25em⁡ P true) − 1 whereas E ads is the average adsorption energy, R = 8.3145 JK –1 Mol –1 is the gas constant, K B = 1.38 × 10 –23 JK –1 is the Boltzmann constant, Δ S represents change in the H 2 entropy from gas to liquid phase, and P is the equilibrium pressure taken to be 1 atm, respectively. − The desorption temperature T D calculated using DFT-D2/D3 is summarized in Table . Additionally, cut-plane plots of electron density difference (EDD) for the 4-12-24H 2 hydrogen-adsorbed h-BN/Gr system are performed to further analyze the interaction between the hydrogen molecules and the h-BN/Gr heterostructure and are presented in Figure (a–c), while rest of the plots are provided in the Supporting Information [refer to Figure S11 (a–d)].…”

“…Such expansion in interlayer distance upon hydrogen molecule adsorption inside the cavity was also observed in bilayer boron nitride. 26,28,91 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 11,33,89,90…”

“…31 A lithium-decorated graphitic carbon nitride monolayer was also reported to be a promising hydrogen storage material with a storage capacity of ∼10.81 wt % and an average adsorption energy of −0.14 to −0.23 eV/H 2 . 32 Majid et al reported that t-graphene-like 2D boron nitride upon alkali decoration can attain up to 12.47 wt % hydrogen storage capacity with an average adsorption energy of −0.217 eV/H 2 and a desorption temperature of 161 K. 33 with a gravimetric density of 10.7 wt %. 34 Light alkalidecorated B, N, C, and berellium (Be) compounds also show promising responses toward hydrogen adsorption.…”