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

Abstract

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–Ti 3 C 2 composites were created in this study by integrating nanoscale nickel (Ni) and Ti 3 C 2 T x MXene nanosheets with Mg particles using a mechanical ball milling process. Compared with incorporating Ni nanoparticles or Ti 3 C 2 T x MXene nanosheets alone, the combination of Ni and Ti 3 C 2 T x MXene enhanced the dehydrogenation performance of magnesium hydride (MgH 2 ). 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/Ti 3 C 2 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/Ti 3 C 2 absorbed 3.16 wt % hydrogen even at 275 °C. The Mg–2Ni/Ti 3 C 2 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 MgH 2 is attributed to the “hydrogen pump” effect of Mg 2 Ni/Mg 2 NiH 4 combined with the catalytic, “facilitated hydrogen pump,” and confinement roles of Ti 3 C 2 T x MXene nanosheets.