Comparison with pc Ru: Finally, we discuss the relevance of our findings derived on Ru(0001) for Ru(pc) electrodes. ORR-CVs and H 2 O 2 CVs recorded on such electrodes in the two electrolytes are presented in Fig. in the SI (note that in this case, the negative potential limit was slightly more positive than in Fig. ). The CVs closely resemble those reported previously, with a steady increase of the ORR current with decreasing potential. Independent of the electrolyte and of the scan direction, the H 2 O 2 formation observed at the collector electrode exhibits a distinct peak between the onset of the ORR and the onset of the HER region. Additionally, the curves for both scan directions are nearly reversible.