Journal of Applied Electrochemistry, Vol.39, No.8, 1217-1227, 2009
Silver-copper electrodeposition from ammonium hydroxide solution: influence of EDTA and HEDTA
The influence of EDTA (ethylenediaminetetraacetic acid, disodium salt) or HEDTA (N-(2-hydroxyethyl)ethylenediaminetriacetic acid, trisodium salt) on silver-copper electrodeposition from ammonium hydroxide solution was investigated. Voltammetric studies showed that silver was deposited at potentials more negative than +0.100 V, while the copper(II) ion was reduced to copper(I) ion and metallic copper at potentials more negative than +0.100 and -0.375 V, respectively. Chronoamperometry, scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS) indicated that, for deposits obtained at -0.450 V, increasing either the silver content in the silver-copper deposit or the charge density of deposition led to dendritic growth. Moreover, dendritic growth decreased when either the EDTA or HEDTA concentration increased. EDS analysis of the deposits obtained at -0.200 V showed codeposition of copper with silver, which was attributed to Cu(I) ion disproportionation to Cu(0) and Cu(II). Moreover, the silver-copper deposits obtained at -0.200 V, from a solution containing EDTA or HEDTA, were non-dendritic in spite of the high silver content. The presence of EDTA and HEDTA improved the silver-copper morphology. X-ray diffraction analysis indicated that the silver-copper electrodeposit was a supersaturated solid solution.