Nano-structured MgH2 catalyzed by TiC nanoparticles for hydrogen storage

BACKGROUND: Magnesium hydride is considered to be a promising hydrogen storage material because of its high gravimetric and volumetric storage capacities. However, its slow kinetics and high desorption temperature of > 300 °C limit practical applications. In this work, TiC nanoparticles were selected to modify the hydrogen storage properties of MgH2. Composite mixtures (MgH2 + TiC) were prepared using both cryogenic milling and high-energy ball milling.  RESULTS: The resulting morphology and crystallite structure of the composites were identified by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The milled samples show good mixing of the hydride and carbide particles, with MgH2 particles around 0.09–1 µm and TiC particles 10–20 nm. The (MgH2 + TiC) composites consist of -MgH2, ß-MgH2 and TiC. MgH2 nano-crystallites of 25 nm were formed after cryomilling. Thermogravimetry reveals that the composites release ~6.5 mass % hydrogen from 190–400 °C at a heating rate of 10 °C min-1 under He flow, with the onset and peak temperatures at 190 and 280 °C, respectively, for the (MgH2 + TiC) after 8 h cryomilling and 60 h ball milling.  CONCLUSION: Results indicate that TiC is an effective catalyst for hydrogen desorption of MgH2.