Selective dissolution of an amorphous Mg65Cu25Y10 alloy in organic acids and dilute HCl solution

• Nanoporous copper can be obtained in organic acids and it does not in dilute HCl.
• Nanoporous copper has a size of nanopores and ligaments less than 20 nm.
• Formic and acetic acids have a buffer ability to prevent the passivation.
• Low mobility and large size of organic acids retard the surface diffusion of Cu adatoms.

Selective dissolution behavior of an amorphous Mg65Cu25Y10 precursor alloy in organic acids has been investigated. Nanoporous copper (NPC) with a pore size of 11–19 nm and ligament of 16–19 nm is obtained after dealloying in 0.01 M formic and acetic acids. NPC formed in formic acid has a larger pore size and similar ligament size than that in acetic acid. Plot of nanopore size versus dealloying time demonstrates the formation of NPC is controlled by the surface diffusion of Cu adatoms. Low diffusion ability of anions with more CH chains from organic acids results in the formation of finer NPCs. On the other hand, NPC is unable to form in 0.01 M HCl solution and corrosion products consist of Y2O3, Y(OH)3, Mg(OH)2 and metallic Cu. The thick corrosion products passivate the surface to prevent from the further aggregation of corrosion. The formation of the finer NPC in organic acids benefits from slow surface diffusion of Cu adatoms, the buffer ability of the organic solutions and the low mobility of the organic molecule.