When similar measurements are performed in O2-saturated electrolyte, we observe a suppression of the electron polaron features until the applied voltage reaches -0.1 V vs. RHE (in comparison to 0.4 and 0.2 V vs. RHE in Ar-saturated electrolyte). Additionally, bipolaronic vibrational bands are not observed in the presence of oxygen, and the neutral band in the Raman spectra does not disappear. These results confirm that electron polaron formation is suppressed through rapid consumption by O2. Notably, no new features were observed in O2saturated electrolyte that could be explained through a surface bound oxygen intermediate. O-O stretching modes for superoxide adsorbates on metals have been reported in the range of ~1000 -1200 cm -1 , which overlaps with one of the neutral p(NDI-T2 P75) Raman modes and, as such, cannot be unequivocally ruled out. However, there is no apparent intensity increase in this region during ORR. Surface bound peroxides have stretching modes at lower wavenumbers, from 640 -900 cm -1 , and we observe no increased Raman intensity in this region. Similar operando spectroscopic results can be observed in 0.1 M KCl (Figure ).