4d-e: The O-upd formed from the dissociation of O2 on Rh(pc) follows a similar power law as on Pt(pc) with a reduced formal potential and a higher value of the interaction parameter 𝑚 &'() . The O2 dissociation is substantially faster on Rh(pc) at over 800 A/cm 2 compared to over 1 A/cm 2 for Pt(pc) on the respective empty surface, accompanied by an increased value of the respective interaction parameter 𝑚 & ( . These findings are qualitatively consistent with a higher surface atom density, increasing the oxygen species' interactions with the metal (attractive) and among each other (repulsive).