First principles guide to tune h-BN nanostructures as superior light-element-based hydrogen storage materials: role of the bond exchange spillover mechanism

Abstract

We investigate the interaction of molecular hydrogen with light element based ndoped hexagonal boron nitride (h-BN) nanostructures and moreover explore the bond exchange mechanism for spillover of atomic hydrogen using dispersion-corrected density functional theory (DFT-D) calculations. A number of doped configurations were tested and it has been found that co-doping of C and O on h-BN sheet significantly increases the adsorption energy of molecular H 2 . The charge transfer from the n-doped h-BN surface to H 2 is found to be the reason for the higher interactions that boosted the binding energy. In addition, the doped h-BN surfaces act as catalysts and dissociate the H 2 molecule with very low activation barrier, but the migration of the resulting H atoms on the surface requires high energy. In order to facilitate easy and fast migration of H atoms, we introduce the bond exchange mechanism using external mediators i.e. borane (BH 3 ) and gallane (GaH 3 ) molecules which serve as a secondary catalysts and help in lowering the migration barrier, leading to the formation of hydrogenated surface. The partially hydrogenated surface in turn can also act as a hydrogen storage material, with a higher propensity to adsorb hydrogen molecules when compared to the unhydrogenated surface. Hence the surface proposed in this work can be used to store substantial quantity of hydrogen as energy source with easy adsorption and desorption kinetics.

Boron Nitride for Hydrogen Storage

“…; in eV) were calculated by using the PW91+D functional (for more details about the calculation method the reader is invited to refer to ref. ). The H 2 –surface distances ( d a ) are in Å.…”

“…This was also confirmed by Kumar et al by using dispersion-corrected DFT. [64] They in addition considered co-doping by Ca nd O, and found that the as-modified BN would be much more efficient in storing H 2 compared with the C-, O-, and 2C-doped counterparts ( Figure 5). Notwithstanding these computational achievements, one may regret av ery limited number of experimental evidences.…”

“…The only work that could be mentioned is about titanium oxide TiO 2 coating BN nanofib- were calculated by using the PW91 + Dfunctional (for moredetails about the calculation method the reader is invited to refer to ref. [64]). The H 2 -surface distances (d a )a re in .Accordingt ot he binding energies, the most efficient configurationfor H 2 adsorption is the C-and O-doped BN, followed by O-doped BN, 2C-dopedB N, and C-dopedB N. Note that the binding energy of "pure" hexagonal BN is À0.15 eV.R eproduced (andadapted) from Ref.…”

“…The H 2 -surface distances (d a )a re in .Accordingt ot he binding energies, the most efficient configurationfor H 2 adsorption is the C-and O-doped BN, followed by O-doped BN, 2C-dopedB N, and C-dopedB N. Note that the binding energy of "pure" hexagonal BN is À0.15 eV.R eproduced (andadapted) from Ref. [64] with permission from The Royal Societyo fChemistry. Figure 6.…”

On the H2interactions with transition metal adatoms supported on graphene: a systematic density functional study

“…8 Far from discourage, further and present research is addressed at enhancing the H 2 attachment to such carbon-based structures. In that sense, analogous boron nitride nanotubes and sheets have been explored, 9,10 with adsorption energies not exceeding 1.25 kJ mol -1 according to DF calculations within the Generalized Gradient Approximation (GGA), yet inclusion of van der Waals (vdW) forces may rise this value up to 14.47 kJ mol -1 in h-BN sheets. 9 Another strategy to enhance the H 2 physisorption to adequate levels is to functionalize the carbon or BN based structures, mostly with light alkaline or alkaline earth metals, where Li, Be, and Ca are probably exemplary cases.…”