Formation of nanoporous copper with hybrid-modal pore size distributions related to surface diffusion of copper atoms during dealloying of Mg 13.5 at.% Cu alloy in an acidic solution

Nanoporous copper (NPC) ribbons with hybrid-modal pore size distributions can be facilely fabricated by effectively controlling the surface diffusivity of Cu atoms during chemical dealloying of dual-phase Mg 13.5 at.% Cu alloy with quasieutectic structures in the HCl solution. These NPC ribbons can be featured by a combination of ligament-pore structures with unimodal pore size distributions at superficial layers and those with bimodal pore size distributions in the interior composed of interconnected large-sized pores with highly porous pore walls. All pores in the ligament-pore structures with unimodal and bimodal pore size distributions are 3D, open and bicontinuous. The formation of the novel NPC ribbons can be well explained as a consequence of the greater diffusivity of Cu atoms at the superficial layers induced by the higher absorbed Cl ^- concentration. According to the ligament sizes, the surface diffusivity of Cu atoms at the superficial layers can be evaluated as 1.68×10 ^-16 m ² s ^-1, which is two orders of magnitude greater than that in the interior of the NPC ribbons (3.55×10 ^-19 m ² s ^-1).