High-value utilization of intermetallic Cu9Al4 as an additive to improve the hydrogen storage performance of magnesium

As a product of in the preparation of Cu–Al clad composites, intermetallic Cu 9 Al 4 greatly affects the mechanical properties of the composites due to its high hardness and poor plasticity, which limits its application. Here, Cu 9 Al 4 is used as an additive to improve the hydrogen storage performance of Mg. Thereby, the Cu 9 Al 4 was introduced into Mg to prepare the Mg‒ x wt.% Cu 9 Al 4 composites ( x = 0, 5, 10, 15, 20 and 25) by high-energy ball milling. The microstructure and phase composition of the composites under different states were analyzed. The hydrogen absorption and desorption kinetics and thermodynamics of the composites at different temperatures are investigated. Compared with pure Mg, the addition of Cu 9 Al 4 can significantly improve the dehydrogenation kinetics of Mg. With the increase of Cu 9 Al 4 content, the hydrogen desorption rate gradually increased. When the Cu 9 Al 4 content was 20 wt.%, the dehydrogenation activation energy calculated according to JMAK kinetic model and Arrhenius equation was the lowest (96.84 kJ mol −1 ), and it had the best hydrogen desorption kinetics. Especially, the phase transition of the first hydrogen absorption process for the Mg‒20 wt.% Cu 9 Al 4 was studied in detail. The results show that the Cu 9 Al 4 phase first transforms into (Cu 1.3 Al 0.7 )Mg during the first hydrogenation, and then Mg reacts with H 2 to generate MgH 2 . In the subsequent dehydrogenation and re-hydrogenation cycles, the (Cu 1.3 Al 0.7 )Mg is stable and does not change. • High-value utilization of intermetallic Cu 9 Al 4 in hydrogen storage materials. • Evolution of the phase structure of Mg ‒ 20 wt% Cu 9 Al 4 composite during hydrogenated. • Intermetallic Cu 9 Al 4 can significantly improve the hydrogen desorption kinetics of magnesium.