First, the Co(II/III) redox couple shifted 91 mV/pH, indicative of a 2e -, 3H + process. This super-Nernstian behavior often signifies that the redox transition is coupled with not only the deprotonation of a group adsorbed on the Co, but also with a more extended deprotonation of sites within the lattice with a pKa of approximately 12, as at this pH value, the magnitude of the redox wave stops increasing . On the other hand, the Co(III/IV) redox wave shifted 63 mV/pH, indicating that this process was a simple 1e -, 1H + (or 2e -, 2H + ) process. The current necessary to attain 10 mA/cm 2 , as measured in galvanostatic mode, showed a shift of 102 mV/pH. Such a dependence of pH on OER catalysis has previously been attributed to a decoupling of proton transfer, electron transfer, and catalytic steps in the OER cycle and has often implied the active role of lattice oxygen in reaction pathway . The next measurement in the series was the use of chemical probes to deduce the presence of particular surface intermediates. We first introduced 1M methanol into the electrolyte as adsorbed nucleophilic *OH groups on metal oxide surfaces were previously found to react with alcohols 36 . Indeed, we observed a slow onset of methanol oxidation just past the Co(II/III) redox transition pointing to the initiation of reactive *OH coverage at this potential value (Fig. ). On the other hand, using 1M tetramethylammonium hydroxide (TMAOH) as the electrolyte, previously argued to specifically interact with active oxygen species and thus hinder the OER cycle , shifted the Co(II/III) redox peak and increased the Tafel slope to 34 mV/dec. This provides evidence for interactions between the Co0.5Fe0.5O0.5F1.5 surface and TMA ions, likely through activated oxygen species.