Considering these recent results and the potential dependent adlayer models proposed in these studies, we revisited the ORR on Ru(0001) in acid, namely HClO 4 and H 2 SO 4 electrolytes. In these electrolytes, the Ru(0001) surface is never free from adsorbates. Part of the adsorbed hydroxyl (*OH) and bisulfate (*HSO 4 ) is only removed below the equilibrium potential for the HER. Therefore, in contrast to former studies, we also explored the ORR in the HER onset potential region. Even though this potential region has no direct technological relevance, it nevertheless is important for the fundamental understanding of the ORR on Ru(0001) and other strongly binding metals.