Influence of Nitrogen Doping into Carbon on the Activation Barrier of ORR in Alkaline Medium: An Investigation Based on Eyring Analysis
Rubul Das, Debittree Choudhury, Rajan Maurya, Shreya Sharma, Manoj Neergat
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 (O 2 to OH – and HO 2 – ) 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 O 2 to HO 2 – is estimated and used in the Eyring analysis to determine the change in enthalpy of activation (Δ H # ). 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 Δ H # at any η. Moreover, Δ H # is a stronger function of η on N/C-900 as compared to that on the carbon surface.