Structure and hydrogen storage properties of MgH2 catalysed with La2O3

The catalytic effect of the addition of lanthanum oxide (La2O3), in the range 0.5-2.0 mol%, on the hydrogenstorageproperties of MgH2 prepared by ball milling has been studied. The addition of La2O3 reduces the formation during milling of the metastable orthorhombic ?-MgH2 phase. The desorption rate of samples with 1 and 2 mol% La2O3 comes out to be about 0.010 wt% per second at 573 K under an hydrogen pressure of 0.3 bar, better than for sample with 0.5 mol% La2O3. The presence of LaH3 after hydrogenation/dehydrogenation cycles has been observed in all samples. The sample with 1 mol% of La2O3 gives a lower hysteresis factor compared with sample with 2 mol%