Effect of Ce element on hydrogen storage property of TiMn₂-based alloys

This study investigates the effect of Ce content on the hydrogen storage properties of Ti_0.98Zr_0.02Mn_1.5Cr_0.05V_0.43Fe_0.09Ce_x (x = 0, 0.02, 0.04, and 0.06) alloys. Microstructural analysis of these alloys revealed dendritic microstructures without the segregation of chemical elements, with the C14 Laves phase identified as the dominant phase. After two activation cycles at 4 MPa and 293 K, the alloys exhibited excellent hydrogen absorption properties. The addition of Ce significantly improved the kinetics of the alloys. At x = 0.02, the hydrogen absorption capacity reached 90% of its maximum within 137 s at 293 K. Pressure–composition–temperature curves indicated that hydrogen absorption capacity initially increased first and then decreased with increasing Ce content, reaching a maximum value of 1.85wt% at x = 0.04. Thermodynamic results demonstrated that the enthalpy and entropy of hydrogen absorption followed a similar trend, which was consistent with the variation in hydrogen storage capacity. Thus, the improvement in hydrogen absorption capacity due to the addition of Ce is attributed to the increase in enthalpy. The increase of the lattice constant in the C14 Laves phase and the deoxidization effect of Ce are expected to be beneficial for the improvement of hydrogen absorption kinetics.