Formation of Nanostructured Gold Sponges by Anodic Dealloying. EIS Investigation of Product and Process

Gold sponges are prepared by anodic leaching of silver from Ag75Au25 alloy sheets in 1 mol L-1 HClO4 solutions. EIS investigations performed after exhaustive dissolution, under blocking conditions, show classical porous behaviour and a capacity, increasing with dissolution potential, in the range 3 to 10 Fg-1. The observed time decrease of capacity is consistent with the occurrence of slow coarsening phenomena. EIS investigations performed during dissolution show a faradaic process in parallel with capacitive charging of the metal sponge, and a much larger capacity. The phenomena are discussed and a simulation is presented, based on a set of plausible parameters.