Study on in situ modification mechanism of mg-Ce-Y based hydrogen storage alloy by ZnF2

The Mg 90 Ce 5 Y 5  +  x wt% ZnF 2 ( x  = 3, 6, 10, 15) composites were prepared by mechanical ball-milling. The effects of ZnF 2 contents on the hydrogen absorption and desorption properties of Mg 90 Ce 5 Y 5 alloy were investigated by XRD , ICP-OES, TEM, PCT and DSC . The excellent hydriding-dehydriding characteristics of the samples after activation were attributed to the catalytic effect of the MgF 2 and MgZn 2 phases introduced in situ by the addition of ZnF 2 . The Mg 90 Ce 5 Y 5  + 6 wt% ZnF 2 composites exhibit the fastest hydrogen adsorption/desorption kinetics and lower decomposition temperatures. At 360 °C, 4.12 wt% H 2 can be absorbed within 180 s, and completely dehydrogenated within 740 s. In addition, the activation energy of dehydrogenation is reduced to 89.5 kJ/ mol, the optimal dehydrogenation temperature is reduced to 318 °C. It is due to the generation of in situ catalysts that weaken the Mg H bond energy, refine the grain sizes , expand specific surface area and increase hydrogen diffusion paths. However, the improvement of the thermodynamics of the composites is limited, the enthalpy is 75.9 kJ/mol H 2 .