Poisoning influence of cyanide on the catalytic oxygen reduction by cobalt(III) tetra(3-methoxy-4-hydroxylphenyl) porphyrin modified electrode

Cobalt(III) tetra(3-methoxy-4-hydroxylphenyl) porphyrin ((CoTMHPP)-T-III) can be irreversibly bound to a platinum electrode through a sol-gel network. Based on our finding that cobalt metalloporphyrin catalyzes dioxygen reduction near 0 mV (vs. Ag/AgCl), the electrocatalytic kinetics of oxygen reduction has been studied by cyclic voltammetry and rotating disk voltammetric methods. A possible reaction mechanism is suggested for the observed catalysis. In the presence of cyanide, the electrocatalytic reductive current for dioxygen is decreased due to the strong binding of cyanide ions to the cobalt metal center. A simplified model is proposed to describe this poisoning effect based on the Koutecky-Levich theory and coordination equilibrium between cyanide and the electrocatalyst. The model is well supported by the experimental results. The poisoning effect can be used for highly sensitive cyanide detection. (C) 2000 The Electrochemical Society. S0013-4651(99)05-073-9. All rights reserved.