Improved hydrogen storage performances of the as-milled Mg-Al-Y alloy by co-doping of Tm@C (Tm = Fe, Co, Cu)

In this study, the porous carbon-based materials loaded with Fe, Co, and Cu nanoparticles were fabricated by chemical blow molding carbonization to ameliorate the hydrogen storage performances of as-milled Mg91Al5Y4 alloy. The Sievert apparatus was utilized to test the isothermal hydrogen absorption/desorption curves and P-C-T (Pressure-composition-temperature) curves. The microstructure characterizations of the specimens were completed by using XRD (X-ray diffraction), SEM (scanning electron microscope), TEM (transmission electron microscope), etc. Besides, Raman spectrum and Nitrogen adsorption/desorption isotherms have been applied to characterize the defect density, specific surface area and dominant pore diameter of the catalysts. Based on the results, the catalysts Tm@C (Tm = Fe, Co, Cu) with porous lamellar structure have the specific surface area of 156.9, 190.9, 106.4 m2/g and the diffraction intensity ratio (ID/IG) of 1.06, 1.09, 0.96, respectively, showing great catalytic influence on hydrogen storage performances of as-milled Mg-Al-Y alloy Concretely, the composite Mg91Al5Y4 + 5 wt% Co@C with the minimum dehydrogenation activation energy of 84.8 kJ/mol can absorb a small amount of H2 at 323 K, besides, the initial hydrogen desorption temperature of it is about 521.5 K. The catalytic functions of Tm@C can be ascribed to the following aspects: the enhancement of milling efficiency and the following particle/grain refinement of alloy; the introduction of great number of defects (active sites); the loaded transition metals (with high electronegativity and multi-valence) or their derivative nanoparticles, etc.