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Influence of Nitrogen Doping into Carbon on the Activation Barrier of ORR in Alkaline Medium: An Investigation Based on Eyring Analysis

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posted on 2023-03-18, 18:05 authored by Rubul Das, Debittree Choudhury, Rajan Maurya, Shreya Sharma, Manoj Neergat
The oxygen reduction reaction (ORR) is investigated on metal-free carbon (Vulcan XC-72) and nitrogen-doped (∼≤1%) carbon (N/C-900) in 0.1 M KOH. The product distribution (O2 to OH and HO2) as a function of overpotential (η) in the temperature range of 293–323 K is analyzed using a rotating ring-disk electrode (RRDE) assembly. The kinetic current due to reduction of O2 to HO2 is estimated and used in the Eyring analysis to determine the change in enthalpy of activation (ΔH#). It is shown that doping of carbon with nitrogen (even with ≤1 wt %) causes substantial increase in the number of active sites (almost 2-fold) and reduction in ΔH# at any η. Moreover, ΔH# is a stronger function of η on N/C-900 as compared to that on the carbon surface.

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