Synergistic Combination of Ni Nanoparticles and Ti3C2 MXene Nanosheets with MgH2 Particles for Hydrogen Storage

Hydrogen storage in the solid state is considered a key technology for developing commercial applications of hydrogen energy. With the addition of efficient nanocatalysts, magnesium (Mg) is a promising approach for overcoming the threshold for hydrogen storage materials. Mg–Ni–Ti3C2 composites were created in this study by integrating nanoscale nickel (Ni) and Ti3C2Tx MXene nanosheets with Mg particles using a mechanical ball milling process. Compared with incorporating Ni nanoparticles or Ti3C2Tx MXene nanosheets alone, the combination of Ni and Ti3C2Tx MXene enhanced the dehydrogenation performance of magnesium hydride (MgH2). The ideal combination of a rapid hydrogen uptake/release rate and high hydrogen storage capability was achieved by properly controlling the proportion of additives. The prepared Mg–2Ni/Ti3C2 composite possessed superior hydrogen storage properties, releasing 3.96 wt % hydrogen at 300 °C, whereas additive-free Mg released almost no hydrogen under the same conditions. Furthermore, Mg–2Ni/Ti3C2 absorbed 3.16 wt % hydrogen even at 275 °C. The Mg–2Ni/Ti3C2 composite exhibited a dehydrogenation activation energy of 75.0 kJ mol–1, which was 60.4 kJ mol–1 less than that of pristine Mg. After 10 cycles, 96.1% of the hydrogen capacity was retained, exhibiting a superior cycling stability. According to the catalytic mechanism study, the surprisingly enhanced hydrogen storage property of MgH2 is attributed to the “hydrogen pump” effect of Mg2Ni/Mg2NiH4 combined with the catalytic, “facilitated hydrogen pump,” and confinement roles of Ti3C2Tx MXene nanosheets.