Kinetics of the ORR on Carbon Materials

On a glassy carbon electrode, the Tafel slope was observed to be 60 mV/dec in alkaline solutions, and at pH 10, the Tafel slope was 120 mV/dec. These values are in accordance with the proposed mechanisms. In the case of 120 mV/dec, the first electron transfer is the rate determining step. In the case of 60 mV/dec, the current-potential relationship observed from the multiple-electron transfer process of ORR on carbon electrodes was expressed as Equation 2.27, given by Taylor and Humffray [14, 17]  

The stoichiometric number y was evaluated from the eurrent-potential measurements in the region of low overpotential, according to the following relation  

On carbon materials, v usually equals 1. Using Allen and Hickling s graphical 

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