Robust Metallic Actuators Based on Nanoporous Gold Rapidly Dealloyed from Gold–Nickel Precursors

Abstract

AbstractDealloyed nanoporous gold (np‐Au) has applications as oxygen reduction catalysis in Li‐air batteries and fuel cells, or as actuators to convert electricity into mechanical energy. However, it faces the challenges of coarsening‐induced structure instability, mechanical weakness due to low relative densities, and slow dealloying rates. Here, monolithic np‐Au is dealloyed from a single‐phase Au25Ni75 solid‐solution at a one‐order faster dealloying rate, ultra‐low residual Ni content, and importantly, one‐third more relative density than np‐Au dealloyed from conventional Au25Ag75. The small atomic radius and low dealloying potential of the sacrificing element Ni are intrinsically beneficial to fast produce high relative density np‐Au, as predicted by a general model for dealloying of binary alloys and validated by experiments. Stable, durable, and reversible actuation of np‐Au takes place under cyclic potential triggering in alkaline and acidic electrolytes with negligible coarsening‐induced strain‐shift. The thermal and mechanical robustness of bulk np‐Au is confirmed by two‐order slower ligament coarsening rates during annealing at 300 °C and 45 MPa macroscopic yielding strength distinctive from the typical early onset of plastic yielding. This article opens a rich direction to achieve high relative density np‐Au which is essential for porous network connectivity, mechanical strength, and nanostructure robustness for electrochemical functionality.