Nanoporous Aluminum by Galvanic Replacement: Dealloying and Inward-Growth Plating

Abstract

In aqueous solutions, electro/chemically deposited metals usually grow outward into electrolyte. Here we report that the reduced Al grows inward into the sample, surprisingly, while Mg (in pure Mg and Al2Mg3 alloy) is galvanically replaced with Al in an ionic liquid. The galvanic replacement reaction (GRR) of Al2Mg3 involves a dealloying process that generates a nanoporous Al skeleton, and simultaneously the inward-growth plating of Al that thickens the Al skeleton. The obtained open nanoporous Al might be interesting for many applications including lithium-ion batteries. The anomalous inward-growth of deposited Al is attributed to the low diffusivity of ionic liquid and the negative charge of reduced species. This dealloying/GRR procedure provides a new route to produce hierarchical nanoporous structure in bulk materials.