Modification of copper foam with silver nanostructures by galvanic replacement

Silver nanostructures were deposited onto the surface of commercially available copper foam (Ag/Cufoam) using the galvanic replacement (GR) method. The regularities of the formation of silver deposits on the copper surface in solutions of hydrated Ag+ ions and [Ag(NH3)2]+ and [Ag(CN)2]– complexes were established. The complex-ion solutions promoted the formation of isle silver nanostructures and a porous film, where the solutions containing hydrated silver ions led to the formation of both isle and dendritic morphologies. During the GR process, the open-circuit potential (OCP) of the Ag/Cufoam shifted toward more positive values by approximately 0.1 V in Ag+ solutions and by 0.25–0.50 V in solutions of silver complexes. The OCP reached a stable value (approx.1 min) and could be considered one of the criteria indicating complete coverage of the foam surface with silver. The morphology of the deposited silver was found to be primarily governed by the precursor concentration and the duration of GR process. SEM revealed the distribution of silver nanostructures over the complex three-dimensional surface of the copper foam. Electrochemical studies of Ag/Cufoam as cathodes for the oxygen reduction reaction (і cathode = 10–20 mAxcm–2 at Е = –0.4 – –0.6 V) demonstrated their high electrocatalytic activity.