Advanced electrochemical characterization of copper deposition

Abstract

The electrodeposition of copper metal in a concentrated sulfuric acid solution is reported to occur through a four-step mechanism: (I) the dehydration of Cu2+ (H2O)6, (II) the reduction of Cu2+ to cu+, (III) the dehydration cu+ (H2O)6-x, (IV) the reduction of Cu+ to copper metal. The dehydration steps have been found to be responsible for the pH-dependence of the electrodeposition reaction. It is also reported, although not well understood, that the presence of Fe2+ ions affects the reaction kinetics. In this work, the kinetics of copper electrodeposition were studied using alternating current cyclic voltammetry. The reaction was studied at a copper rotating disk electrode with varying concentrations of Cu2+ and Fe2+ . At sufficiently low pH, and a sufficiently high concentration of Fe2+ , the deposition kinetics may be slowed enough to separately observe the two electron transfer steps involved in copper reduction. It was found that Fe2+ ions affect the electrodeposition kinetic by slowing down reaction kinetics, particularly the second electron transfer reaction.