Improved hydrogen storage kinetics and thermodynamics of RE-Mg-based alloy by co-doping Ce–Y

Abstract

Aiming at improving hydrogen storage performance of Mg-base alloy, the Mg90Ce5Y5 alloy, which has high capacity and high stability, was prepared by vacuum induction melting. The XRD, SEM, TEM, PCI, and DSC were used to characterize the microstructure and phase transformation of alloy as well as hydrogen storage property. The results indicate that the Mg90Ce5Y5 alloy consists of multiphase structure, including the CeMg12, Y5Mg24, Ce2Mg17 as well as residual Mg phase, besides, part Y dissolved in both Mg and CeMg12/Ce2Mg17 phase to form solid solutions. After hydrogen absorption, these phases transform into the MgH2, CeH2.73 and YH2 phase, while after hydrogen desorption, the MgH2 transforms into the Mg phase, but the rare earth hydride phase was not changed. There is another reversible transformation between the CeH2.73 and CeO2 phase, which is beneficial for the cyclic stability of the alloy. The alloy has the reversible hydrogen capacity of about 6.0 wt% H2 as well as the activation energy of 114.3 kJ/mol, and also exhibits enhanced kinetics compared with the pure MgH2 sample, as a result of the synergistic effect of rare earth hydride phase. Meanwhile, it is also noted that the Mg90Ce5Y5 alloy begins to release hydrogen below 250 °C and the rate of hydrogen desorption is mainly dominated by surface controlled.