Photoélectrochimie des phtalocyanines sans métal, de cuivre et de fer

Abstract

The cathodic and photocathodic behavior of electrodes of phthalocyanines without metal or complexed to copper or iron (H2Pc, CuPc, and FePc) has been studied in acidic, neutral, and alkaline media. In the dark, the polarization curve of the electrode of FePc shows two peaks of reduction which are not observed with the other phthalocyanines; these are associated with the reduction of the central cation. Lighting the semiconducting electrodes does not produce any effect on the reaction of production of hydrogen. An analysis of the curves of capacity vs. potential indicates the presence of intermediate levels localized within the forbidden band of the semiconductors and covering about 1% of their sites on the surface. The results can be explained if the phthalocyanines are considered to be semiconducting electrodes of type p. The energy of the bands and of the surface states can be depicted with a semiconductor–electrolyte interphase model and the nature of the charge transfers inhibited by the presence of these interfacial states is discussed. [Journal translation]