Kinetics and Mechanism of Oxygen Electroreduction in Acidic and Neutral Solutions on Carbon Black XC-72R Modified by Products of Pyrolysis of Cobalt 5,10,15,20-Tetrakis(4-Methoxyphenyl)Porphyrin

Cathodic oxygen reduction on the XC-72R carbon black modified by the products of pyrolysis of cobalt 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin (CoTMPP) (XC-72M) was studied in acidic and neutral electrolytes. Formation of new active centers on XC-72M is confirmed by voltammetric curves (specific charge density grows as compared to the XC-72R carbon black by 2-2.5 times) using the methods of rotating disk electrode (a shift in half-wave potential E-1/2 by 600 mV) and rotating ring-disk electrode (the fraction of the direct reaction increases to 70%). Herewith, the partial derivative E-1/2/partial derivative PH value in the range of pH 0.3-8.5 is -60 mV. It is shown that proton necessarily participates in the slow stage of the first electron transfer for the further occurrence of the direct reaction to water. At a transition from acidic solutions to neutral ones, the polarization curves converge for XC-72M and XC-72R, which is due to a decrease in the concentration of proton in the solution and variation of the mechanism of the oxygen reduction slow stage.