Defects induced metallized boron hydride monolayers as high-performance hydrogen storage architecture

Abstract

Experimental synthesis of two-dimensional boron hydride monolayer (BH-ML) (J. Am. Chem. Soc. 2017, 139, 13,761) has motivated us to explore its application in clean energy storage. We have performed first-principles calculations based on spin-polarized density functional theory (DFT) to investigate the ground-state geometries, electronic structures, metal doping mechanism and hydrogen (H2) storage propensities of BH-ML. Pristine BH-ML barely binds H2, however the introduction of selected light metal dopants, such as Na, Ca, and Sc, improved the H2 adsorption mechanism tremendously. Binding energies of dopants under maximum doping concentration are found as −1.51, −2.49, and −4.54 eV for Na, Ca, and Sc, respectively, which are strong enough to ensure their uniform distribution over BH-ML without clustering. Each dopant donated bulk of its charge to BH-ML and transforms into cation and anchored multiple H2 molecules through electrostatic and van der Waals interactions. We have found that a maximum of 24H2 molecules could be adsorbed on BH-ML decorated with four metal dopants of Na, Ca, and Sc. Average adsorption energies of H2 are found within desirable range. Our results show that Na, Ca, and Sc decorated BH-ML could reach to exceptionally high H2 storage capacities of 14.84, 12.28, and 11.70%, respectively, which easily surpass the US Department of Energy (DOE) target of 5.50 wt% by 2025. We have further applied thermodynamic analysis to explain the H2 storage proficiencies at practical conditions of temperatures and pressures. Our report confirms that BH-ML decorated with light metal dopants are ideal option for high-capacity H2 storage applications.