A comparative study for synthesis methods of nano-structured (9Ni–2Mg–Y) alloy catalysts and effect of the produced alloy on hydrogen desorption properties of MgH2

• Various methods for preparing (9Ni–2Mg–Y) catalyst were investigated.
• Effect of produced (9Ni–2Mg–Y) on H2 desorption properties of MgH2 was studied.
• Addition of (9Ni–2Mg–Y) compound on MgH2 decreased the H2 desorption temperature.
• Addition of (9Ni–2Mg–Y) compound on MgH2 improved the H2 desorption kinetics.
• H2 desorption improved by decreasing the particle size of catalyst.

9Ni–2Mg–Y alloy powders were prepared by arc melting, induction melting, mechanical alloying, solid state reaction and subsequent ball milling processes. The results showed that melting processes are not suitable for preparation of 9Ni–2Mg–Y alloy due to high losses of Mg and Y. Therefore, 9Ni–2Mg–Y alloy powder was prepared by three methods including: 1) mechanical alloying, 2) mechanical alloying + solid state reaction + ball milling, and 3) mixing + solid state reaction + ball milling. The prepared 9Ni–2Mg–Y alloy powders were compared for their catalytic effects on hydrogen desorption of MgH2. It is found that 9Ni–2Mg–Y alloy powder prepared by mechanical alloying + solid state reaction + ball milling method has a smaller particle size (1–5 μm) and higher surface area (1.7 m2 g−1) than that of other methods. H2 desorption tests revealed that addition of 9Ni–2Mg–Y alloy prepared by mechanical alloying + solid state reaction + ball milling to MgH2 decreases the hydrogen desorption temperature of MgH2 from 425 to 210 °C and improves the hydrogen desorption capacity from 0 to 3.5 wt.% at 350 °C during 8 min.