Microstructural optimization with Mo addition for enhanced hydrogen desorption in cost-effective Ti–Cr-(FeV80) alloys

Efficient and low-cost hydrogen storage alloys are essential for advancing hydrogen energy applications. V-based BCC alloys possess high theoretical hydrogen storage capacity, yet their widespread application is hindered by the high cost of pure vanadium. In this study, a cost-effective Ti-Cr-(FeV80) alloy system was developed by partially substituting pure V with the FeV80 master alloy, while Mo was incorporated to optimize the microstructure due to the impurities from FeV80 and further enhanced hydrogen desorption performance. The Ti 40 Cr 32 (FeV80) 28 -Mo alloys exhibited improved plateau pressures and enhanced hydrogen storage properties compared with alloys prepared from pure V. Among them, the Ti 40 Cr 32 (FeV80) 28 - 9wt% Mo alloy delivered an effective desorption capacity of 2.2 wt% at 348 K with a dehydrogenation activation energy as low as 42.88 kJ·mol -1 , following a diffusion-controlled mechanism. Moreover, the 9 wt% Mo alloy demonstrated excellent cyclic durability, maintaining superior capacity retention over 100 cycles. Microstructural analysis revealed that Mo addition effectively homogenizes the alloy by mitigating impurity-induced segregation, which suppresses the formation of Ti-rich phases. Density functional theory (DFT) calculations further revealed that Mo substitution decreases hydride stability (formation energy -0.0545 eV/atom vs. -0.0727 eV/atom for the Mo-free alloy), thereby weakening metal-hydrogen bonds and facilitating dehydrogenation. This integrated experimental and theoretical study demonstrates that Mo addition is a viable strategy for tuning the structure-property relationship of FeV80-based BCC alloys, providing valuable insights into the design of economical, durable, and high-performance hydrogen storage materials.