Phase‐Engineered V‐Mo‐La Alloying Enables Room‐Temperature Activation and Highly Reversible Hydrogen Storage in TiFe‐Based Alloys

ABSTRACT TiFe‐based AB‐type alloys are among the most promising candidates for solid‐state hydrogen storage, offering high theoretical capacity, moderate plateau pressure, and low raw‐material cost from earth‐abundant constituents. However, their large‐scale deployment remains hindered by sluggish room‐temperature activation and progressive cycling‐induced capacity degradation. Here, a phase‐existence‐form‐guided strategy is developed to balance activation, usable capacity, and durability by assigning V and Mo as B2‐matrix solutes and La to secondary/interfacial regions. V promotes hydrogen transport, Mo improves desorption reversibility and stabilizes the matrix, and La‐rich regions play a key role in enabling room‐temperature activation. The optimized Ti 1.05 Fe 0.94 V 0.02 Mo 0.04 La 0.02 alloy directly absorbs hydrogen at 298 K without high‐temperature pretreatment and, in its fully activated state, delivers an effective capacity of 1.88 wt.% under 9.5 MPa absorption and 328 K/0.1 MPa desorption conditions, retaining 96.89% of its maximum capacity after 800 cycles. DFT calculations reveal that V lowers the hydrogen migration barrier, whereas multiscale post‐cycling analyses show that Mo mitigates defect accumulation, local amorphization, and particle pulverization. These findings establish phase‐existence form as a transferable design principle for balancing room‐temperature activation, usable capacity, and long‐term durability in AB‐type hydrogen storage alloys.