Cobalt tetra(4-N N′N″-trimethylanilinium)porphyrin (CoTMAP) has been studied in aqueous solutions using cyclic voltammetry, differential pulse voltammetry as well as by RRDE and spectroelectrochemical methods. The CoIII/CoIITMAP couple dissolved in 0.05 mol dm-3 H2SO4 has a redox potential of +0.14 V. The λmax of the Soret band are 427 and 412 nm for CoIII and CoIITMAP, respectively. The rate constant for the reaction between CoIITMAP and dioxygen in 0.05 mol dm-3 H2SO4 was estimated to be 3 × 107 dm3 mol-1 s-1. The CoIIITMP has been found to absorb at monolayer levels on glassy carbon surfaces and to have a catalytic effect on dioxygen electroreduction in aqueous solutions. This catalytic effect is strongly dependent on electrolyte pH. The overvoltage of O2 reduction is reduced by 480 mV and insignificant amounts of H2O2 are produced at pH 1, while an overvoltage decrease of 300 mV and an H2O2 yield of 70% are observed at pH 8.
ASJC Scopus subject areas
- Chemistry (all)