Naturally, the universality of these findings is of substantial interest. Therefore, this analysis has been expanded to other metals exhibiting O-upd features (Fig. ), such as the fcc-metal rhodium, iridium, palladium, and gold. Except for Au, the metal surfaces facilitate the ORR and reach the mass transport (MT) limitation of the transport of molecular oxygen (Fig. ), allowing the extraction of the MT-corrected ORR activities displayed in the common Tafel plot (Fig. ). At this point one must acknowledge the individual challenges of these different metallic surfaces: The O-upd formation on Ir(pc) is smeared out and extends into the H-upd region making the correct determination of its associated charge difficult and leading to an unacceptable uncertainty.