Electrochemical Properties of a Porphyrin-Cobalt (II) Adsorbed on Silica–Titania–Phosphate Composite Surface Prepared by the Sol–Gel Method

Abstract

SiO2/TiO2/phosphate was obtained by the sol–gel processing method, having the following characteristics: specific surface area SBET=800 m2 g−1, Ti=14.8 wt% and P=1.5 wt%, and ion exchange capacity of 0.58 mmol g−1. The tetrakis(1-methyl-4-pyridyl) porphyrin ion, H2TmPyP4+, was immobilized on the matrix surface by an ion exchange reaction and then metallated in situ with Co(II), resulting in SiO2/TiO2/phosphate/CoTmPyP material. The amount of CoTmPyP incorporated to the matrix was 35.0 μmol g−1. Cyclic voltammetry studies and rotating disk electrode experiments using a carbon paste electrode made with the material were carried out. The immobilized complex catalyzed O2 reduction to H2O at −0.22 V in 1 mol L−1 KCl solution at pH 6.8. The cathodic current intensities plotted against O2 concentrations, between 1 and 11 ppm, showed a linear correlation.