Hydrogen storage in Mg 2 Ni(Fe)H 4 nano particles synthesized from coarse-grained Mg and nano sized Ni(Fe) precursor.

In this work, Mg 2 Ni(Fe)H 4 was synthesized using precursors of nano Ni(Fe) composite powder prepared through arc plasma method and coarse-grained Mg powder. The microstructure, composition, phase components and the hydrogen storage properties of the Mg-Ni(Fe) composite were carefully investigated. It is observed that the Mg 2 Ni(Fe)H 4 particles formed from the Mg-Ni(Fe) composite have a diameter of 100-240 nm and a portion of Fe in the Ni(Fe) nano particles transformed into α-Fe nano particles with the diameter of 40-120 nm. DSC measurements showed that the peak desorption temperature of the Mg 2 Ni(Fe)H 4 was reduced to 501 K and the apparent activation energy for hydrogen desorption of the Mg 2 Ni(Fe)H 4 was 97.2 kJ mol -1 H 2 . The formation enthalpy of Mg 2 Ni(Fe)H 4 was measured to be -53.1 kJ mol -1 H 2 . The improvements in hydrogen sorption kinetics and thermodynamics can be attributed to the catalytic effect from α-Fe nano particles and the destabilization of Mg 2 NiH 4 caused by the partial substitution of Ni by Fe, respectively.