The catalytic reactions in the Cu–Li–Mg–H high capacity hydrogen storage system

Abstract

A family of hydrides, including the high capacity MgH2 and LiH, is reported. The disadvantages these hydrides normally display (high absorption/desorption temperatures and poor kinetics) are mitigated by Cu-hydride catalysis. This paper reports on the synthesis of novel CuLi0.08Mg1.42H4 and CuLi0.08Mg1.92H5 hydrides, which are structurally and thermodynamically characterized for the first time. The CuLi0.08Mg1.42H4 hydride structure in nanotubes is able to hold molecular H2, increasing the gravimetric and volumetric capacity of this compound. The catalytic effect these compounds show on hydride formation and decomposition of CuMg2 and Cu2Mg/MgH2, Li and LiH, Mg and MgH2 is analyzed. The Gibbs energy, decomposition temperature, and gravimetric capacity of the reactions occurring within the Cu-Li-Mg-H system are presented for the first time. First principles and phonon calculations are compared with experiments, including neutron spectroscopy. It is demonstrated that the most advantageous sample contains CuLi0.08Mg1.92 and (Li) ∼ Li2Mg3; it desorbs/absorbs hydrogen according to the reaction, 2CuLi0.08Mg1.42H4 + 2Li + 4MgH2 ↔ 2CuLi0.08Mg1.92 + Li2Mg3 + 8H2 at 114 °C (5.0 wt%) - 1 atm, falling within the proton exchange membrane fuel cell applications window. Finally the reaction 2CuLi0.08Mg1.42H4 + MgH2 ↔ 2CuLi0.08Mg1.92 + 5H2 at 15 °C (4.4 wt%) - 1 atm is found to be the main reaction of the samples containing CuLi0.08Mg1.92 that were analyzed in this study.

Metal hydrides: an innovative and challenging conversion reaction anode for lithium-ion batteries

“…The reactions of 2MgH 2 + M (M = Cu, Si) and 0.65Mg + 0.35M (M = ScH 2 , Ti) mixtures prepared by reactive grinding under 90 bar of hydrogen pressure with lithium ions were also studied [ 19 , 25 – 27 ]. The electrochemical behavior of MgH 2 is not affected by the presence of a second element, Cu or Si, and significant reversible capacities for the conversion process (>1000 mA·h·g −1 ) are obtained.…”

Fabrication of Multiple-Phase Magnesium-Based Hydrides with Enhanced Hydrogen Storage Properties by Activating NiS@C and Mg Powder

“…17,18 Among them, multiphase Mg-based hydrides possessed more thermal instability than the single MgH 2 phase. 19,20 However, the reduction of the hydrogen storage capacity for multiphase Mgbased hydrides is the major deficiency that needs to be addressed. Facing this problem, a simple and effective method is to establish MgH 2 -rich complex hydrides, such as MgH 2 − Mg 2 NiH 4 , which exhibits significant thermodynamic instability without an obvious loss in capacity.…”

“…In the past few years, researchers had tried many approaches to accelerate the thermodynamics and kinetics of MgH 2 , such as nanocrystallization, , alloying, − adding catalysts, − and constructing complex hydrides systems. , Among them, multiphase Mg-based hydrides possessed more thermal instability than the single MgH 2 phase. , However, the reduction of the hydrogen storage capacity for multiphase Mg-based hydrides is the major deficiency that needs to be addressed. Facing this problem, a simple and effective method is to establish MgH 2 -rich complex hydrides, such as MgH 2 –Mg 2 NiH 4 , which exhibits significant thermodynamic instability without an obvious loss in capacity .…”

Enhanced H2 sorption performance of magnesium hydride with hard-carbon-sphere-wrapped nickel

“…[5][6][7][8][9][10][11] One of these methods involves alloying with transition metal elements (e.g., Mg 2 Ni); Mg-based alloys exhibit better thermal instability of hydrides than pure magnesium. [12][13][14][15] However, the unavoidable loss of hydrogen storage capacity is the major drawback of the alloying route due to the addition of a transition metal. To solve this problem, a benecial solution is to build MgH 2 -rich complex hydrides, 16 i.e., MgH 2 -Mg 2 NiH 4 composites, which exhibit a considerable reduction in stability without a clear loss in capacity.…”

“…, Mg 2 Ni); Mg-based alloys exhibit better thermal instability of hydrides than pure magnesium. 12–15 However, the unavoidable loss of hydrogen storage capacity is the major drawback of the alloying route due to the addition of a transition metal. To solve this problem, a beneficial solution is to build MgH 2 -rich complex hydrides, 16 i.e.…”