Percolation effects with copper electrodeposition in ion-exchange material

The effect of preliminary doping of sulfo cation-exchange material KU-23 15/100S with a chemically deposited metal (Ag, Cu) on the rate of copper ion electroreduction is investigated. It is shown that the threshold dependence of the reaction current of copper electroreduction on the amount of doped metal is due to the formation of a single percolation cluster in an ion-exchange grain and, as a result, to the appearance of electron conductivity. It is established that preliminary doping changes the nucleation mechanism from a gradual to an instantaneous one. Results from a local X-ray spectral microanalysis provide the basis for concluding that copper electrodeposition is uniform throughout the volume of an ion-exchange grain. The average size of the copper particles formed is 100 nm.