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) c an be irreversibly bound to a platinum electrode through a sol-gel network. Based on our finding that cobalt metalloporphyrin catalyzes dioxygen reduc tion near 0 mV (vs. Ag/AgCl), the electrocatalytic kinetics of oxygen reduc tion has been studied by cyclic voltammetry and rotating disk voltammetric methods. A possible reaction mechanism is suggested for the observed cataly sis. In the presence of cyanide, the electrocatalytic reductive current for dioxygen is decreased due to the strong binding of cyanide ions to the cob alt metal center. A simplified model is proposed to describe this poisoning effect based on the Koutecky-Levich theory and coordination equilibrium be tween cyanide and the electrocatalyst. The model is well supported by the e xperimental results. The poisoning effect can be used for highly sensitive cyanide detection. (C) 2000 The Electrochemical Society. S0013-4651(99)05-0 73-9. All rights reserved.