Abstract
Mg90Ce5Y5 + x wt % Yb2O3 (x = 2, 4, 6, 8, 10, 20) samples were prepared by high energy ball milling. The kinetic and thermodynamic properties of the composites were investigated by XRD, TEM, SEM, EDS and PCT. And all samples were tested for hydrogen absorption and desorption. The Mg90Ce5Y5 + 10 wt % Yb2O3 sample displays the fastest hydrogen uptake rate, namely full hydrogenation takes only 125 min at 473 K. And it can fully dehydrogenate in just 75.6 min at 553 K. In addition, the value of Edes is reduced to 95.5 kJ/mol. The improvement of dynamic performance is due to the change of microstructure: Yb2O3/YbH2, YH2 and CeO2 provide plenty of active sites, and abundant defects and grain boundaries lead to the emergence of many high-energy regions and diffusion channels. The ∆H value of Y10 (77.6 kJ/mol H2) is not significantly lower than Mg90Ce5Y5, indicating that the addition of Yb2O3 do not improve the thermodynamic properties.
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