Structural and kinetic investigation of the hydride composite Ca(BH₄)₂ + MgH₂ system doped with NbF₅ for solid-state hydrogen storage

Abstract

Designing safe, compact and high capacity hydrogen storage systems is the key step towards introducing a pollutant free hydrogen technology into a broad field of applications. Due to the chemical bonds of hydrogen-metal atoms, metal hydrides provide high energy density in safe hydrogen storage media. Reactive hydride composites (RHCs) are a promising class of high capacity solid state hydrogen storage systems. Ca(BH4)2 + MgH2 with a hydrogen content of 8.4 wt% is one of the most promising members of the RHCs. However, its relatively high desorption temperature of ∼350 °C is a major drawback to meeting the requirements for practical application. In this work, by using NbF5 as an additive, the dehydrogenation temperature of this RHC was significantly decreased. To elucidate the role of NbF5 in enhancing the desorption properties of the Ca(BH4)2 + MgH2 (Ca-RHC), a comprehensive investigation was carried out via manometric measurements, mass spectrometry, Differential Scanning Calorimetry (DSC), in situ Synchrotron Radiation-Powder X-ray Diffraction (SR-PXD), X-ray Absorption Spectroscopy (XAS), Anomalous Small-Angle X-ray Scattering (ASAXS), Scanning and Transmission Electron Microscopy (SEM, TEM) and Nuclear Magnetic Resonance (NMR) techniques.

Design of a Nanometric AlTi Additive for MgB2-Based Reactive Hydride Composites with Superior Kinetic Properties

“…Under dynamic conditions the dehydrogenation reaction occurs in a steps reaction: 2LiBH 4(l) + MgH 2(s) → Mg (s) + 2LiBH 4(l) + H 2(g) → 2LiH (s) + MgB 2(s) + 4H 2(g) 17 . Additionally, as also observed in other RHC systems [18][19][20][21][22] , the Li-RHC system reacts via different pathways depending on the temperature and pressure conditions and requires an appropriate hydrogen overpressure during the dynamic 5 dehydrogenation process to assure the reversibility of the hydrogen uptake-release process 23,24 . In the last decade, several studies have been conducted to investigate the effect of transition metal .…”

A comprehensive study on lithium-based reactive hydride composite (Li-RHC) as a reversible solid-state hydrogen storage system toward potential mobile applications

“…12,19 The reaction-enthalpies of various systems were altered by using the this concept. [20][21][22][23][24][25][26][27][28][29] In this work, MgH 2 is used to stabilize the dehydrogenation products of LiBH 4 . Indeed, the overall reaction enthalpy of the LiBH 4 -MgH 2 reactive hydride composite system (Li-RHC) is reduced to 46 kJ mol À1 H 2 , 12 in comparison to the respective values of each single metal hydride (LiBH 4 (67 kJ mol À1 H 2 ), MgH 2 (75 kJ mol À1 H 2 )), 5,30 according to the following reaction path:…”

Enhanced Hydrogen Storage Properties of Li-RHC System with In-House Synthesized AlTi3 Nanoparticles

“…Long-lasting improvements of the kinetic properties of complex hydrides and RHCs can be achieved by using transition metals (TM)-based additives [36,[45][46][47][48][49][50][51][52][53][54]. Several investigations on the effect of the addition of TMbased additives on the kinetic properties of the RHCs have been conducted [45,46,50,[55][56][57][58][59][60][61]. In most cases, the added components reacted with the hydride system during milling, forming more stable TM compounds.…”