Effect of Er2O3 on kinetic and thermodynamic properties of RE-Mg based hydrogen storage alloys

Abstract

In this paper, Mg90Ce5Y5 alloy was prepared by vacuum induction melting and Er2O3 catalyst was doped by high energy ball milling. The phase structure and microstructure were characterized by XRD, TEM, EDS, and the results showed that the ball-milled samples contained CeMg12, Ce2Mg17, Y5Mg24, Mg and Er2O3. After hydrogen absorption, the phase composition is MgH2, CeO2, YH2, Er2O3 and ErH3. Only MgH2 and ErH3 participated in the dehydrogenation reaction to form Mg and ErH2 phase, and other phases have excellent thermodynamic stability. Moreover, there are abundant defects inside the composite particle. In the process of hydrogenation, the E6 sample absorbs 84.3% of maximum hydrogen (4.65 wt % H2) in 573 K within 2 min, which has more excellent hydrogen absorption kinetics than the others, especially Mg90Ce5Y5 (64.7%). The E6, E8 and E10 composites desorbs 3 wt %H2 at 20.2, 22.2 and 19.9 min in 573 K, respectively, and the Edes of them is 76.9 ± 1.8, 80.4 ± 0.4 and 78.4 ± 1.2 kJ/mol, respectively. The kinetics of dehydrogenation does not increase with the increase of catalyst content. The thermodynamic properties have not been significantly improved, but because the existence of ErH2 ↔ ErH3 reversible reactions has been weakly improved.