Effect of rare earth doping on the hydrogen storage performance of Ti1.02Cr1.1Mn0.3Fe0.6 alloy for hybrid hydrogen storage application

In order to improve the activation behavior of Ti1.02Cr1.1Mn0.3Fe0.6 alloy with high hydrogen desorption pressure for hybrid hydrogen storage vessel application, the rare earth (RE) doped Ti1.02Cr1.1Mn0.3Fe0.6RE0.03 (RE = La, Ce, Ho) alloys were prepared by induction levitation melting. The effect of rare earth doping on the microstructures and hydrogen storage properties was also investigated systematically. The results show that Ti1.02Cr1.1Mn0.3Fe0.6 alloy displays a single C14 Laves phase, and there is a secondary phase of rare earth oxide in the RE doped alloys. The RE doping strategy can expand the unit cell volume of C14 Laves main phase. After RE doping, the activation behavior of the Ti1.02Cr1.1Mn0.3Fe0.6RE0.03 alloy is obviously improved and the hydrogen storage capacity is increased, while the hydrogen desorption plateau pressure is decreased. Moreover, the RE-free alloy can hardly absorb hydrogen at room temperature under 34-43 MPa hydrogen pressure, but all RE-doped alloys can absorb hydrogen to saturation under the same condition. The decline of pressure plateau is inversely proportional to the atomic number of RE. Among the studied alloys, the Ti1.02Cr1.1Mn0.3Fe0.6La0.03 alloy shows the best overall properties and can be fully activated at room temperature. Its hydrogen absorption pressure is 39.31 MPa and 51.27 MPa under 298 K and 318 K, respectively. Its hydrogen storage capacity is up to 1.715 wt% and the dissociation enthalpy is 16.63 kJ/mol H2 with a desorption plateau slope of 0.098.