Dehydrogenation mechanism of ball-milled MgH2 doped with ferrites (CoFe2O4, ZnFe2O4, MnFe2O4 and Mn0.5Zn0.5Fe2O4) nanoparticles

Ferrites (CoFe2O4, ZnFe2O4, MnFe2O4 and Mn0.5Zn0.5Fe2O4) nanoparticles can all significantly reduce the desorption temperature of MgH2, and CoFe2O4 shows the best catalytic performance among the four ferrites. After dehydrogenation, new by-products including Mg, Co3Fe7 and MgO phases are found for the CoFe2O4 doped samples, and Mg, Fe3Zn10, Fe and MgO phases are identified for the ZnFe2O4 doped samples. Mg, Fe, Mn and MgO phases are observed for the MnFe2O4 doped samples, while Mg, Fe3Zn10, Mn, Fe and MgO phases appear for the Mn0.5Zn0.5Fe2O4 doped samples. New forming phases Co3Fe7, MgO and Co also have a great catalytic effect on the MgH2 hydrogen storage properties. The onset desorption temperature of MgH2 doped with bimetallic catalysts (20 wt.% Co + 20 wt.% MgO and 20 wt.% Co3Fe7 + 20 wt.% MgO) is lower than that of MgH2 doped with the single catalyst (40 wt.% Co, 40 wt.% MgO and 40 wt.% Co3Fe7), indicating that MgO and Co or MgO and Co3Fe7 have the combination catalytic function.