Abstract
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.
Published Version
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