Modifying the hydrogen storage performances of NaBH4 by catalyzing with MgFe2O4 synthesized via hydrothermal method

Abstract

In this study, the hydrogenation performance of NaBH4 was modified by the addition of 10 wt% MgFe2O4 as the catalyst. The NaBH4 + 10 wt% of MgFe2O4 sample was prepared by a ball milling technique. The onset decomposition temperature of MgFe2O4-doped NaBH4 was decreased to 323 °C and 483 °C for the first and second stage of dehydrogenation as compared to the milled NaBH4 (497 °C). The desorption kinetics study showed that the addition of MgFe2O4 caused the sample to had faster hydrogen desorption with a capacity of 6.2 wt% within 60 min while the milled NaBH4 had only released 5.3 wt% of hydrogen in the same period of time. For the isothermal absorption kinetics, the total amount of hydrogen absorbed by the milled NaBH4 was 3.7 wt% while the NaBH4 + 10 wt% MgFe2O4 sample showed better absorption characteristic with a total amount of 4.5 wt% of hydrogen within 60 min. The calculated desorption activation energy from the Kissinger plot of NaBH4 + 10 wt% MgFe2O4 sample was 187 kJ/mol which reduced by 28 kJ/mol than the milled NaBH4 (215 kJ/mol). The in-situ formation of MgB6 and Fe3O4 after the dehydrogenation process indicates that these new species were responsible for the improved hydrogenation performances of NaBH4.