A Pd–Pt-based bulk nanoporous alloy with continuous solubility for hydrogen

Metal hydrides that enable reversible solute exchange with a reservoir often exhibit a miscibility gap at room temperature. Misfit strain during two-phase coexistence may then lead to degradation on repeated charging/discharging cycles. Furthermore, the miscibility gap impairs continuous and uniform composition tuning for functional applications. We explore electrochemical dealloying as a pathway to macroscopic monolithic samples of nanoporous Pd–Pt with continuous solubility for H at room temperature. The ligament size is tunable in the range of 4–40 nm, and sorption isotherms suggest a miscibility-gap critical point marginally below room temperature. With a maximum hydrogen fraction of 0.5, we demonstrate a reversible actuation strain of 3.3 % and a high cycle stability. • A nanoporous metal hydride is developed with continuous solubility of hydrogen for a large interval of hydrogen fraction. • The preparation protocol achieves macroscopic specimens with ligament diameters tunable from 4 to 40 nm. • The absence of a miscibility gap avoids defect accumulation during charging/discharging cycles, providing for high cycle stability.