Asynchronous Evolution of Nanoporous Silver on Dual-Phase Ag–Sn Alloys by Potentiostatic Dealloying in Hydrochloric Acid Solution

Evolution behavior of the nanoporous architectures has been investigated via potentiostatic electrochemical dealloying of dual-phase Ag(x)Sn(100−x) (x = 20, 30, 40 at.%) alloys, which consist of β-Sn and ε-Ag(3)Sn phases with different volume fractions in 1.2 M HCl solution. The results show that the open-circuit potentials and corrosion potentials of dual-phase Ag–Sn alloys are determined by the less noble β-Sn phases rather than chemical compositions of the Ag–Sn precursor alloys. The potentiodynamic polarization curves show that the anodic dissolution of Ag–Sn alloys is divided into two stages including the first preferential dissolution of β-Sn phases and secondary dealloying of ε-Ag(3)Sn phases, which is associated with the order of the nanoporous evolution. Nanoporous silver (NPS) can be fabricated by potentiostatic dealloying of dual-phase Ag–Sn alloys in HCl solution. The dealloying of two phases is asynchronous: The less noble β-Sn phases are preferentially etched to generate the larger pores, and then the more noble ε-Ag(3)Sn phases are dealloyed to form the finer nanoporous structure. The significant surface diffusion of Ag adatoms at the applied potential higher than the pitting potential of ε-Ag(3)Sn phases during the dealloying results in the coarsening of nanoporous ligaments with a time dependence of d(t) [Formula: see text] t(0.1). The fractions and the difference in electrochemical stabilities of the β-Sn and ε-Ag(3)Sn phases in dual-phase Ag(x)Sn(100−x) (x = 20, 30, 40 at.%) precursor alloys determines the final nanoporous structure.