Iron and nitrogen codoped carbon catalysts (Fe/N/C catalysts) are promising nonprecious-metal catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. Understanding the ORR kinetics over Fe/N/C catalysts is crucial for active catalyst development. Here, we propose an analytical method for rotating ring窶電isk electrode (RRDE) voltammetry to separate the ORR for O2 reduction to H2O via the 4-e pathway (k1), O2 reduction to H2O2 via the 2-e pathway (k2), H2O2 reduction to H2O via the 2-e pathway (k3), H2O2 chemical decomposition to O2 and H2O (k4), and H2O2 oxidation to O2 by the 2-e pathway (k窶�2). First, RRDE voltammetry in an H2O2 solution was performed, yielding k3, k4, and k窶�2. The obtained parameters were used to analyze the ORR voltammogram to calculate I1窶ｲ, I2窶ｲ, I3窶ｲ, I4窶ｲ, k1窶ｲ, and k2窶ｲ. These currents and kinetic constants were corrected by studying the effect of the catalyst loading density to obtain I10, I20, I30, I40, k10, and k20, thus avoiding the overestimation of I10 and k10 caused by the quasi-four-electron reduction of O2. The contribution of k4 during the ORR is negligible at considerable anodic and cathodic overpotentials but was detected at 0.8 V, for which k3 and k窶�2 are relatively small.
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