Effect of Cr and Mo Substitution of Fe on Activation and Hydrogen Ab-/Desorption Properties of TiFe Hydrogen Storage Alloy

In this study, a series of quaternary TiFe-based alloys, Ti1.05Fe0.85Cr0.1-xMox (x = 0, 0.03, 0.05, 0.07, 0.1), were designed to investigate the activation and hydrogen ab-/desorption properties of TiFe hydrogen storage alloys through the substitution of Fe with Cr and Mo. The incorporation of Cr and Mo significantly enhanced the activation performance of TiFe hydrogen storage alloys, enabling activation at room temperature. This improvement in activation was accompanied by the maintenance of a high maximum hydrogen storage capacity and an elevated effective hydrogen storage capacity. As the Mo content increased, the lattice parameters increased slightly, further boosting the activation performance and reducing the optimal operating temperature from 90 to 75 degrees C, which can be readily matched using the waste heat from fuel cells. The addition of Mo also resulted in a flatter hydrogen absorption plateau, making the hydrogen storage and release process more stable. Among the alloys, Ti1.05Fe0.85Cr0.05Mo0.05 exhibited the best performance, with a maximum hydrogen storage capacity of 2.00 wt.%, an effective hydrogen storage capacity of 1.81 wt.%, and a relatively flat hydrogen ab-/desorption plateau. After 200 cycles, the hydrogen storage capacity decreased by only 0.50%, indicating promising application prospects in related fields.