We finally discuss an indirect effect of the local field due to surface coverage as Pt(111)bound H 2 O species increasingly desorb under operating ORR potentials. We tentatively propose that this effect promotes a dissociative-type mechanism that breaks the O-O bond already during the first step of the catalytic mechanism. Our results thus overall suggest a more complex mechanistic picture than hitherto anticipated; one where the local field may manifest in different, yet potentially equally important, ways over different systems.