Electrochemical and spectroelectrochemical (SERS) studies of the reduction of methylene blue on a silver electrode

The electrochemical behavior of methylene blue (MB+) on a silver electrode has been investigated by cyclic voltammetry, the rotating disk electrode technique, chronoamperometry and surface-enhanced Raman spectroscopy (SERS). The electrochemical results have shown that MB+ is reduced in two one-electron steps and that these two reduction processes are, at least partially, controlled by mass transport. The electrochemical measurements have also shown that the reduction of MB+ on the surface of a silver electrode promotes the formation of two different films. The SERS spectra have shown the presence of distinct species on the electrode surface as the potential is made more negative. Such a dependence on the potential allowed the characterization of the chemical species associated with the first and second film formation. They are, respectively, the radical cation (HMB. +) and leucomethylene blue (LMB). (C) 2002 Elsevier Science B.V. All rights reserved.