Hydrogen storage properties of Li–Mg–N–B–H/ZrCoH3 composite with different ball-milling atmospheres

Abstract

Li–Mg–N–B–H/ZrCoH3 composites were successfully synthesized by ball milling of the reactants under argon and hydrogen atmosphere, respectively. The composite synthesized by reactive ball milling (RBM) under hydrogen has the best hydrogen storage properties. It can desorb 3.71 wt% hydrogen in 60 min at 150 °C under pressure of 0.1 MPa, and the dehydrogenation capacity reaches 4.59 wt% in 8 h. For the re-hydrogenation, 5.27 wt% hydrogen was absorbed in only 10 min at 150 °C under H2 pressure of 8 MPa. The phases of the as-milled and subsequently dehydrogenated and re-hydrogenated samples were determined by X-ray diffraction (XRD). The microstructures and elemental distributions were characterized by scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS) measurements. It is shown that Mg is in situ hydrogenated and introduced homogeneous distribution of ZrCoH3 particles during the RBM process under hydrogen atmosphere. The activation energies for the composites were calculated by Kissinger method through differential scanning calorimetric (DSC) measurements for the dehydrogenation process with different heating rates. It is determined that the activation energy for the Li–Mg–N–B–H/ZrCoH3 composite synthesized by RBM under hydrogen is 79.9 kJ·mol−1, which is 14 kJ·mol−1 lower than that for the sample without ZrCoH3 addition. The N–H bond energies were analyzed by infrared (IR) absorption spectrum, and the reasons for weakening of the N–H bond were further discussed.