Nanostructured Ti-catalyzed MgH2 for hydrogen storage

Nanocrystalline Ti-catalyzed MgH2 can be prepared by a homogeneously catalyzed synthesis method. Comprehensive characterization of this sample and measurements of hydrogen storage properties are discussed and compared to a commercial MgH2 sample. The catalyzed MgH2 nanocrystalline sample consists of two MgH2 phases-a tetrahedral beta-MgH2 phase and an orthorhombic high-pressure modification gamma-MgH2. Transmission electron microscopy was used for the observation of the morphology of the samples and to confirm the nanostructure. N-2 adsorption measurement shows a BET surface area of 108 m(2) g(-1) of the nanostructured material. This sample exhibits a hydrogen desorption temperature more than 130 degrees C lower compared to commercial MgH2. After desorption, the catalyzed nanocrystalline sample absorbs hydrogen 40 times faster than commercial MgH2 at 300 degrees C. Both the Ti catalyst and the nanocrystalline structure with correspondingly high surface area are thought to play important roles in the improvement of hydrogen storage properties. The desorption enthalpy and entropy values of the catalyzed MgH2 nanocrystalline sample are 77.7 kJ mol(-1) H-2 and 138.3 J K-1 mol(-1) H-2, respectively. Thermodynamic properties do not change with the nanostructure.