Controlling the deposition of silver and bimetallic silver/copper particles onto a carbon nanotube film by electrodeposition-redox replacement

The electrodeposition-redox replacement (EDRR) process was studied to control the creation of copper and silver containing particles on the surface of a carbon nanotube film. Synthetic solutions simulating typical hydrometallurgical copper electrolysis process solutions (40 g/L Cu, 120 g/L H₂SO₄) with different dilute concentrations of silver (1–10 ppm) were utilized as the source for particle deposition and recovery. Such process solutions are currently underutilized for use as a potential source for the deposition of noble particles. The effect of deposition voltage, deposition time, stirring, and redox replacement time between deposition pulses were investigated as the parameters affecting the morphology and composition of the deposited particles as well as deposition kinetics. The results showed that pure copper particles can be deposited when the redox replacement time between deposition pulses is very short (t = 2 s). By increasing the redox replacement time (t = 50 s and more) the original copper particle composition transforms into a core-shell structure with an outer layer predominately consisting of silver or a bimetallic mix of copper and silver, depending on the deposition conditions. The bimetallic Cu/Ag particle size could be controlled from 200 to 840 nm by the applied deposition voltage. At high redox replacement times (t = 150 s and more) the resulting particles were shown to be pure silver with a small diameter from 100 to 250 nm.