(a) ORR Polarization Curves
(b) H2O2 Reduction Reaction (HPRR)
(c) Ring Current
Figure 5: ORR activity of FeTPP/C catalyst (pyrolyzed at 800°C) in O2 saturated acidic and alkaline electrolytes. (a) ORR polarization curves, (b) hydrogen peroxide reduction reaction (HPRR) in comparison to ORR, and (c) ring current. All measurements were performed at 900 rpm rotation rate and 20 mV/s scan rate. = 1.1 V versus RHE in 0.1 M NaOH and = 1.3 V versus RHE in 0.1 M HClO4. HPRR is shown in oxygen-free electrolytes containing externally added H2O2 at a concentration of 3.5 mM. Also shown in (c) is the ring current profile of 30% Pt/C in 0.1 M NaOH for comparison.