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 α-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.