Study of the dehydrogenation behavior of magnesium hydride

Hydrogen sorption properties of a MgH2–10wt.% graphite mixture

“…These differences can be explained by the coexistence of Mg and MgH 2 in each desorbing particle for global hydrogen contents below 4.5 wt.% [10,11,23]. Following the ideas presented for MgH 2 without additives in [10,11], the observed behavior can be rationalized by considering that the incompletely hydrided samples contain Mg islands that grow during dehydriding and make metal nucleation unnecessary. Additionally, these islands provide a preferential desorption path that permits the H surface recombination to become the rate limiting process.…”

“…Thus, considering how the partially hydrided samples were obtained it can be assumed that the hydride is preferentially located near the surface (see schemes in Fig. 3) and [10]. In contrast, at intermediate stages of the complete desorption curve the hydride is mainly located near the centre of the particles, due to the fact that the material was fully hydrided at the beginning and desorption proceeds by the growth of Mg nuclei formed on the surface [10].…”

“…3) and [10]. In contrast, at intermediate stages of the complete desorption curve the hydride is mainly located near the centre of the particles, due to the fact that the material was fully hydrided at the beginning and desorption proceeds by the growth of Mg nuclei formed on the surface [10]. Therefore, in this last case the hydrogen atoms must diffuse through the Mg matrix to reach the surface, whereas in the partially hydrided samples the hydrogen atoms can get to the surface much faster by diffusing along the Mg/MgH 2 interphase.…”

“…Despite the efforts made, no consensus has been reached on the rate limiting steps on hydrogen absorption and desorption in Mg and Mg based materials. Absorption and desorption rates have been found to be controlled by nucleation and growth mechanisms, by the surface, by diffusion or by the interphase reaction [3][4][5][6][7][8][9][10][11]. Additionally, though several papers have shown that carbon and carbon allotropes have a beneficial effect on hydrogen sorption in Mg [12][13][14][15][16][17][18][19][20][21], the role that carbon plays in these processes has not yet been clearly established.…”

Agile Thermal Management STT-RX, Modified Magnesium Hydride and Calcium Borohydride for High-Capacity Thermal Energy Storage (PREPRINT)

“…Ni is chosen as the catalyst because of its ability to break hydrogen bonds during hydrogenation and enhance recombination of hydrogen atoms during dehydrogenation, and Ni catalyzed MgH 2 reactions have shown better kinetics and lower decomposition temperatures than other transition metals [9,10,11 ].…”