A benign route to fabricate nanoporous gold through electrochemical dealloying of Al-Au alloys in a neutral solution

Nanoporous gold (NPG) ribbons have been fabricated through electrochemical dealloying of melt-spun Al-Au alloys with 20-50 at.% Au in a 10 wt.% NaCl aqueous solution under potential control at room temperature. The microstructures of NPG were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDX) analysis. The microstructures of the NPG ribbons strongly depend upon the phase constitutions of the starting Al-Au alloys. The single-phase Al2Au or AlAu intermetallic compound can be fully dealloyed, resulting in the formation of NPG with a homogeneous porous structure. The separate dealloying of Al2Au and AlAu in the two-phase Al-45 Au alloy leads to the formation of NPG composites (NPGCs). In addition, the dealloying of the Al-20 Au alloy comprising alpha-Al and Al2Au leads to the formation of NPG with bimodal channel size distributions. According to the ligament size, the surface diffusivity of Au adatoms along the alloy/electrolyte interface has been evaluated and increases with increasing applied potential. The dealloying mechanism in the neutral NaCl solution has been explained based upon pourbaix diagram and chloride ion effect. (C) 2009 Elsevier Ltd. All rights reserved.