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

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.