Refinement of Nanoporous Copper by Dealloying MgCuY Amorphous Alloys in Sulfuric Acids Containing Polyvinylpyrrolidone

Nanoporous Cu was fabricated by dealloying Mg65Cu25Y10 amorphous alloy in a mixed solution of poly-vinylpyrrolidone (PVP) and sulfuric acid. A significant change was observed in the pore and ligament size when dealloying in the mixed solution rather than in a 0.1 M H2SO4 solution free of PVP: in the mixed solution containing 10 g/L PVP the mean sizes of pores and ligaments were 10 nm and 14 nm, whereas they were 66 nm and 84 nm in the PVP-free solution. With increasing concentration of PVP in the dealloying solutions, the size of nanopores and ligaments decreased in the following manner: the decrease was small in the PVP concentration range of 0 to 0.1 g/L (Type I), and large in the 0.1 to 10 g/L range (Type II). A decrease in the surface diffusivity of more than three orders of magnitude was noted with the addition of 10 g/L PVP. This can be explained by the restrictions on free diffusion of Cu adatoms due to the adsorption of PVP macromolecules which force Cu adatoms to diffuse in a relatively narrower range, and thus smaller Cu ligaments and nanopores formed. The introduction of organic macromolecule into dealloying solution helps refine nanoporous structures. (C) 2014 The Electrochemical Society. All rights reserved.