Chloride ion effect and alloying effect on dealloying-induced formation of nanoporous AuPt alloy

The dealloying of the rapidly solidified Al66Au23.8Pt10.2 precursor in the 5 wt.% HCl or 20 wt.% NaOH solution has been investigated using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and transmission electron microscopy, in order to clarify the chloride ion effect and alloying effect on the formation of nanoporous Au–Pt alloy. The Al66Au23.8Pt10.2 precursor is composed of a single Al2Au-type intermetallic compound and only Au(Pt) solid solution can be identified in the as-dealloyed sample. The Pt addition can significantly refine the nanoporous structure during the dealloying of the Al66Au23.8Pt10.2 precursor either in the HCl or NaOH solution. Moreover, the alloying effect of Pt markedly exceeds the coarsening effect of chloride ion adsorption for the formation of nanoporous Au–Pt. The average ligament size is 5.2 ± 0.7 and 3.3 ± 0.4 nm for the nanoporous Au–Pt alloy obtained in the HCl and NaOH solution, respectively. In addition, electrochemical measurements including potentiodynamic polarization and cyclic voltammetry have also been performed on the Al66Au23.8Pt10.2 precursor.