Asynchronous Evolution of Nanoporous Silver on Dual-Phase Ag⁻Sn Alloys by Potentiostatic Dealloying in Hydrochloric...

Evolution behavior of the nanoporous architectures has been investigated via potentiostatic electrochemical dealloying of dual-phase Ag_xSn_100-x (x = 20, 30, 40 at.%) alloys, which consist of β-Sn and ε-Ag₃Sn 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-Ag₃Sn 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-Ag₃Sn 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-Ag₃Sn phases during the dealloying results in the coarsening of nanoporous ligaments with a time dependence of d(t) ∝ t^0.1. The fractions and the difference in electrochemical stabilities of the β-Sn and ε-Ag₃Sn phases in dual-phase Ag_xSn_100-x (x = 20, 30, 40 at.%) precursor alloys determines the final nanoporous structure.