Enhanced Hydrogen Ab/De-sorption of Mg(Zn) solid solution alloy catalyzed by YH2/Y2O3 nanocomposite

Abstract

YH2/Y2O3 nanocomposite was prepared and introduced to Mg0.97Zn0.03 solid solution alloy forming a nanocomposite of Mg0.97Zn0.03-10 wt%YH2/Y2O3 by mechanical milling. The phase components and microstructure were systematically investigated by XRD, SEM and STEM. Hydrogenation of Mg0.97Zn0.03 solid solution resulted in phase segregation into MgH2 and intermetallic compound MgZn2. The in-situ formed ultra-fine MgZn2 homogeneously dispersed in MgH2 matrix, and returned to Mg(Zn) solid solution through dehydrogenation. This reversible phase transition of Mg(Zn) solid solution benefited to thermodynamic destabilization of MgH2. The co-dopant of YH2 and Y2O3 exhibited synergistic catalytic effects on the hydrogen absorption and desorption of Mg0.97Zn0.03 solid solution alloy. As a result, Mg0.97Zn0.03-10 wt%YH2/Y2O3 nanocomposite showed significantly improved kinetics with obviously lowered hydriding and dehydriding activation energy of 45.8 kJ⋅mol−1⋅H2 and 74.7 kJ⋅mol−1⋅H2, respectively, and the enthalpy of hydrogen desorption was reduced to 72.2 kJ⋅mol−1⋅H2.