Electrochemical properties of porphyrin-doped polypyrrole films

Abstract

Meso-tetra-(4-sulfonatophenyl)-porphin (TPPS 4) has been incorporated into polypyrrole (PPy) films as a dopant-anion during electropolymerisation from aqueous solutions. The addition of TPPS 4 to the polymerisation solution increases the rate of electropolymerisation substantially, changes the morphology markedly, and increases the redox-activity of the PPy films formed. This catalytic effect of the TPPS 4 on the rate of electropolymerisation was established in the case of non-metallized porphyrin; it means that the effect is not caused by the influence of redox-active metal-ions inserted into the porphin centre. Insertion of the Co 2+ ions into the porphin centres was carried out from acetate solutions with high efficiency (70%) even in the case of thick (3–10 μm) TPPS 4 doped PPy films. Well-developed waves connected with the Co 2+/3+ transition taking place in meso-tetra-(4-sulfonatophenyl)-porphyrinato cobalt (II) (CoTPPS 4) were established. The voltammograms measured in an air atmosphere show that the electrocatalytic reduction of molecular oxygen starts at the same potential as the wave of Co redox-transition. The PPy films have been characterised by cyclic voltammetry, SEM, AFM, and X-ray microanalysis.