Scanning Electrochemical Microscopy: Study of the Deposition and Stripping Mechanism of Lead in the Presence of Copper

This paper describes the application of scanning electrochemical microscopy (SECM) in the substrate-generation/tip-collection (SG/TC) mode to elucidate mechanistic aspects of the deposition and stripping of Pb2+ ions in the presence of Cu2+ into a glassy carbon substrate electrode. A stripping peak was observed between the main peaks corresponding to the pure metals. Its position, height and shape were investigated, and the peak intensity was found to depend on the Pb2+/Cu2+ concentration ratio. The results suggested that this peak was due to the dissolution of lead deposited in copper, as a result of an underpotential deposition. The scanning electrochemical microscope provided additional information towards the understanding of the stripping mechanisms in analytical studies. In particular, the SECM-tip response yielded direct evidence about the speciation of some of the compounds evolved during stripping. This information was not available from the voltammetric response of the substrate electrode alone.