The in situ spectroelectrochemical experiment shows that an absorption peak at 580.5 nm attributable to poly(methylene blue) grows slowly at the beginning of the electrolysis of methylene blue, and then this peak grows more quickly. The visible spectra prove that there are two absorption peaks at 580.5 and 690.2 nm respectively for the mixture solution after electrolysis. The former one indicates that poly(methylene blue)polymerized on the ITO electrode is partly soluble; the latter one is attributed to a water-soluble polymer since it completely dissolves in the aqueous solution. The result from the rotating ring-disk electrode identifies that an intermediate is produced at the disk electrode, which is collected at the ring electrode. The ring current increases with decreasing the ring potential and with increasing the rotation rate. Thus, the intermediate is a species carrying a positive charge and not too stable.The result from the XPS experiment shows that the anions can be doped into poly(methylene blue) film and dedoped from it during oxidation and reduction processes. The results from the impedance experiment indicate that the charge transfer impedance of poly(methylene blue) decreases with decreasing potential.
