Bimetallic Fe–V catalyzed magnesium films exhibiting rapid and cycleable hydrogenation at 200 °C

We examined hydrogen sorption in 1.5 μm thick Mg–Fe–V films, using the binary alloys as baselines. At 200 °C both Mg–V and Mg–Fe–V absorb in tens of seconds, and desorb in tens of minutes. The ternary alloys show minimal kinetic or capacity degradation even after 105 absorption/desorption cycles. Pressure—composition isotherms yield the well-known enthalpies of α-MgH2 formation (decomposition), agreeing with x-ray diffraction results. The x-ray spectrum also shows a broad hump centered near (011) reflection of CsCl-type Fe–V phase. Our hypothesis is that a densely distributed nanoscale Fe–V acts both as a potent hydrogen dissociation catalyst and a heterogeneous nucleation site.