Abstract
We have shown previously that the addition of In and C enhances the hydrogen desorption capacity and considerably improves the kinetics of hydrogen desorption from Mg-Ni based alloys, important from the perspective of hydrogen storage. In this paper, we present the results of tests of the long-term stability of the sorption behaviour of these materials. We studied how the capacity and sorption kinetics changed 5 years from the preparation of two chosen Mg-Ni-In-C alloys differing in indium concentration. Kinetic curves and PCT isotherms were measured at temperatures of 250–350 °C. It was found that long-term storage of the hydrogen-charged samples led to no significant downgrade in hydrogen sorption kinetics. However, the absorption capacity somewhat decreased from about 5 wt.% H2 to about 3 wt.% H₂ due to partial phase decomposition. Relatively intensive tentative oxidation during preparation, which had a slightly beneficial effect on the desorption rate of freshly-prepared samples, caused almost total blocking of hydrogen sorption in the aged samples.

Key words
hydrogen, hydrogen storage, magnesium alloys, indium

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