Novel NLi4-BGra/MgH2-based heterojunctions for efficient hydrogen storage and modulation of hydrogen-desorption temperature ranges

Abstract

In this study, a novel superalkali NLi4 decorated Boron doped graphene/magnesium hydride heterojunction NLi4-BGra/MgH2 was designed using density functional theory (DFT). Molecular dynamics (MD) confirmed that this material can release H2 adsorbed near NLi4 and H stored within MgH2 at a fixed hydrogen-desorption temperature (Td) of 298 K and 570 K, respectively. Subsequently, 132 magnesium alloy hydrides Mg1-XMeXH2 with various hydrogen-storage capacities and hydrogen-desorption temperatures were predicted by DFT combined with machine learning (ML). Among them, Mg0.875Li0.125H2 (Td = 400K) and Mg0.875Be0.125H2 (Td = 500K) were selected to form NLi4-BGra/Mg0.875Me0.125H2 (Me = Li, Be). The successful validation of Root Mean Square Deviation, diffusion coefficient and hydrogen-desorption trajectories to qualify the hydrogen-desorption capability of NLi4-BGra/Mg0.875Me0.125H2 (Me = Li, Be) (Td = 400, 500K) confirms that the strategy of using Mg1-XMeXH2 to substitute MgH2 in NLi4-BGra/MgH2 enables the effective modulation of the hydrogen-desorption temperature ranges of NLi4-BGra/MgH2-based heterojunctions. In particular, partial density of state, electron localization function, and charge density difference were comprehensively analyzed to understand the hydrogen-storage mechanism and the nature of the hydrogen-desorption temperature variation.