In the positive-going scan, the current largely follows the previous scan, except for a hysteresis in regions IIIa and IIa, in the range between 0.1 V and the onset of the ORR at 0.6 V, where the cathodic current starts to decrease earlier than in the negative-going scan. A similar behavior was also reported by Inoue et al.. In contrast to their data, our ORR-CVs contain a few wavelike structures in the increasing / decreasing ORR current that seem to be correlated with the redox features in the BCV in Fig. . Based on our own previous measurements, we suggest that the difference between the two studies is probably related to the surface preparation, i.e., to a higher defect density of the Ru(0001) surfaces used in the former study, the way how the electrochemical measurements were performed, and the design of the electrochemical cell.