Effect of different complexing agents on Pb–Co thin-film electrodeposition

Lead (Pb)–cobalt (Co) films have been studied by several researchers regarding their electrocatalytic activity when used as anodes in oxygen evolution reactions. Although several authors have suggested that the electrodeposition technique is the best alternative to Pb–Co film deposition, the process is complex. In many cases, the use of complexing agents facilitates the electrodeposition of multi-element coatings; but this performance has not been reported in the literature for Pb–Co electrodeposition. In this work, the effect of three different complexing agents (tartaric acid, sodium citrate, and ascorbic acid) on Pb–Co electrodeposition was studied. Speciation diagrams and polarization curves have been used to determine the reduction potentials of Pb 2+ and Co 2+ ions in the different systems studied. Speciation diagram predictions were incapable of revealing all species present in solution and for an accurate prediction of the actual electrochemical functioning of the system; the information given by the speciation diagrams and polarization curves must be considered together. Additionally, electrodeposition of Pb–Co films was achieved without complexing agent and using the three complexing agents. Morphological and chemical properties of these coatings are shown and discussed in terms of the electrochemical functioning of each system. Finally, the electrocatalytic ability of the Pb–Co films was investigated by means of polarization curves.