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

A family of hydrides, including the high capacity MgH 2 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 CuLi 0.08 Mg 1.42 H 4 and CuLi 0.08 Mg 1.92 H 5 hydrides, which are structurally and thermodynamically characterized for the first time. The CuLi 0.08 Mg 1.42 H 4 hydride structure in nanotubes is able to hold molecular H 2 , increasing the gravimetric and volumetric capacity of this compound. The catalytic effect these compounds show on hydride formation and decomposition of CuMg 2 and Cu 2 Mg/MgH 2 , Li and LiH, Mg and MgH 2 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 CuLi 0.08 Mg 1.92 and (Li) ∼ Li 2 Mg 3 ; it desorbs/absorbs hydrogen according to the reaction, 2CuLi 0.08 Mg 1.42 H 4 + 2Li + 4MgH 2 ↔ 2CuLi 0.08 Mg 1.92 + Li 2 Mg 3 + 8H 2 at 114 °C (5.0 wt%) - 1 atm, falling within the proton exchange membrane fuel cell applications window. Finally the reaction 2CuLi 0.08 Mg 1.42 H 4 + MgH 2 ↔ 2CuLi 0.08 Mg 1.92 + 5H 2 at 15 °C (4.4 wt%) - 1 atm is found to be the main reaction of the samples containing CuLi 0.08 Mg 1.92 that were analyzed in this study. Cu-Li-Mg-H novel hydrides and catalytic processes will open new vistas in the field of storage for both hydrogen and batteries.