Hydrogen absorption in Ni-catalyzed Mg: A model for measurements in the low temperature range

•Hydrogen absorption in Mg at low and intermediate temperatures was studied.•A model was proposed and the activation energy of the system was calculated.•The model reproduced accurately the absorption kinetics.•At low temperatures, diffusion is the controlling mechanism.•A mechanism transition at intermediate temperatures was found.

Magnesium has been deeply studied as a possible hydrogen storage material for both, mobile and static applications. In this article we continued the work presented in our previous paper by modeling the hydrogen absorption in Ni-catalyzed magnesium in the range of pressures of 500 kPa–5000 kPa and temperatures from 423 K to 468 K. A new model based in the Ginstling–Brounshtein diffusion equation was proposed for the hydrogen absorption kinetics. It adds the contribution of the pressure of the gaseous phase and the enthalpy of reaction to the previously mentioned diffusive model. An activation energy for the process was estimated and the value obtained (112 kJ/mol) was concordant with previous values reported in the literature.

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