title: Electrochemical Properties of a Porphyrin-Cobalt (II) Adsorbed on Silica-Titania-Phosphate Composite Surface Prepared by the Sol-Gel Method.
abstract: SiO(2)/TiO(2)/phosphate was obtained by the sol-gel processing method, having the following characteristics: specific surface area S(BET)=800 m(2) 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, H(2)TmPyP(4+), was immobilized on the matrix surface by an ion exchange reaction and then metallated in situ with Co(II), resulting in SiO(2)/TiO(2)/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 O(2) reduction to H(2)O at -0.22 V in 1 mol L(-1) KCl solution at pH 6.8. The cathodic current intensities plotted against O(2) concentrations, between 1 and 11 ppm, showed a linear correlation. Copyright 2000 Academic Press.
authors.affiliation: Instituto de Química, Unicamp, Campinas, SP, 13083-970, Brazil
authors.initials: AM
authors.lastname: Castellani
authors.initials: Y
authors.lastname: Gushikem