Previous work has established that when a few volume percent of transition metal-based particles are dispersed in nano-grained MgH 2 powders, H-sorption times are reduced to a few minutes at temperatures near 300 °C. We report H-sorption cycles performed in a mini-tank of Mg powders containing such particle dispersions placed in monochromatised synchrotron light going through the powders for in situ X-ray diffraction in transmission at the European Synchrotron Radiation Facility. The three selected catalyst particle dispersions were Nb 2O 5, FeF 3 and amorphous Ti 0.7Ni 0.3. The main result is that these very different 2nd phase particle additions have a similar impact on H-sorption in the sense that in all three MgH 2 powders, H-sorption goes to completion as T ≈ 270 °C reached during heating. The commonality of the three selected particle dispersions, two crystalline and one amorphous, is that their thermodynamic properties are consistent with the chemical conditions of immiscibility and H-attractive interfaces within MgH 2 powders. Once this condition is satisfied, the acceleration of the kinetics of sorption is likely dominated by the extent (specific area) of such internal interfaces.
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