Improving the Air Poisoning Resistance of V–Ti–Cr–Fe Hydrogen Storage Alloys through Pd-Mediated Hydrogen Dissociation

Surface poisoning caused by trace air severely degrades the cycling durability of V-based hydrogen storage alloys. Herein, we demonstrate that minor addition of Pd (i.e., 0.5–1 at. %) significantly enhances the air poisoning resistance of V75Ti11Cr13Fe1 alloys while preserving their hydrogen storage capacity. Pd atoms are incorporated into the alloy lattice without the formation of a secondary phase and function as “hydrogen-entry windows,” suppressing surface oxidation. Consequently, the alloys containing 0.5–1 at. % Pd retain approximately 70% of their hydrogen storage capacity after 10 cycles in H2 containing 250 ppm air, contrasting with the mere 7.5% of the pristine alloy. This work provides an effective strategy for improving the air stability of V-based hydrogen storage alloys.