Leveraging Atomic Disorder to Modulate Hydrogen Storage Thermodynamics in Intermetallics

Abstract

Hydrogen storage in metal hydrides holds great promise for advancing a low-carbon energy future. Yet, fine-tuning the thermodynamics of hydrogen absorption remains challenging with traditional microalloying approaches. Here, we report a strategy inspired by compositionally complex alloy design to introduce atomic disorder into the prototypical TiFe intermetallic system. By progressively substituting Fe with Co, Ni, Cu, and Mn in equal proportions, we synthesize a series of near-single-phase B2-structured compositionally complex intermetallics, that is, Ti₅₀(FeCo)₅₀, Ti₅₀(FeCoNi)₅₀, Ti₅₀(FeCoNiCu)₅₀, and Ti₅₀(FeCoNiCuMn)₅₀ (at.%). These materials exhibit hydrogen storage capacities (measured by pressure-composition isotherm, PCI) of 1.39, 1.42, 1.31, and 1.14 wt.% under 100 bar of H₂ at 50°C, respectively. Notably, Ti₅₀(FeCo)₅₀ demonstrates rapid hydrogen uptake kinetics, achieving 90% of its full capacity within 77 s under 50 bar of hydrogen pressure at 50°C. Hydrogen storage thermodynamic analyses reveal that increasing atomic disorder stabilizes the hydride phase, with thermodynamic stability following the order: Ti₅₀(FeCoNiCuMn)₅₀ > Ti₅₀(FeCoNi)₅₀ > Ti₅₀(FeCoNiCu)₅₀ > Ti₅₀(FeCo)₅₀. Our findings establish atomic disorder as a versatile thermodynamic tuning knob for intermetallic hydrides, offering a rational framework for the design of advanced hydrogen storage materials.