Enhanced hydrogen sorption properties of core-shell like structured Mg@NaBH4/MgB2 composite

To improve the hydrogen sorption properties of Mg, an arc plasma method with a vacuum vapor deposition technique was used to synthesize a core-shell like structured Mg@NaBH 4 composite. Homogeneously distributed nanoscale NaBH 4 particles can be observed on the surface of Mg matrix according to bright-field scanning transmission electron microscope (BF-STEM) and high-resolution transmission electron microscopy (HRTEM) techniques. A solid solution of Na in Mg might form according to the results of XRD and energy dispersive X-Ray analysis (EDX)-STEM technique. The hydrogenation activation energy ( E a  = 60.1 kJ/mol H 2 ) of the Mg in the composite and the onset dehydrogenation temperature for the hydrogenated composite measured from temperature programmed desorption (TPD) (245 °C) were lower than those of pure MgH 2 . The improvement can be ascribed to the core-shell like structure which induces more sufficient contacts between catalysts and Mg, thus providing more nucleation sites for hydrogen sorption. In addition, the formation of MgB 2 and the substitution of Na atoms might support more grain boundaries and cause the changes of electronic structure of Mg/MgH 2 , which can significantly improve the hydrogen sorption properties of Mg. This study implies a novel structure design approach for development of future hydrogen absorption materials.