Epoxy-infiltrated hierarchical nanoporous Cu with exceptional ductility and surface-enabled functions

• Hierarchical nanoporous Cu with epoxy infiltration enhances tensile ductility. • Large surface area retained after epoxy infiltration for functional applications. • Electrochemical actuation strain of composite close to monolithic nanoporous Cu. • A new strategy overcomes brittleness while preserving functional properties. The large surface area of dealloyed nanoporous metals has enabled novel functional properties including catalysis, energy conversion and storage, actuation and sensing. Nevertheless, the practical application of these materials is hindered by their extreme brittleness under tension and bending. Filling the nanopores with polymer may enhance their ductility; however, it eliminates the large open surface area and thereby leads to the loss of the aforementioned functionalities. In this study, we fabricated a hierarchical nanoporous Cu with micron-scale pores at the higher hierarchical level and nanoscale pores at the lower level. By infiltrating the large pores with epoxy, we obtained a material that combines excellent mechanical stability with surface-enabled functionalities. In this material, the soft and ductile epoxy network suppresses crack propagation during deformation, enhancing the fracture strain from nearly zero to 46 % under tension. Meanwhile, the nanoporous structure remains open and offers a large surface area that is crucial for functionalities. For example, the electrochemical actuation behavior of a hierarchical nanoporous Cu dose not change significantly when its large pore channels are infiltrated with epoxy. This study presents a strategy to overcome the brittleness of dealloyed nanoporous materials while retaining the large surface area, thus paving the way for the practical applications of this new type of functional materials.