) via the 2e -ORR is pretty straightforward after forming HOOH* via the peroxide pathway (iii). Figure (c) tells us that the adsorbate's direct desorption as H 2 O 2 occurs spontaneously under reaction conditions, while continued onsurface dissociation towards OH*+OH* is an activated process. We establish this latter result using umbrella sampling simulations with O-O distance as the CV and predict a small, yet existing, ca. 0.3 eV barrier around -0.2 V vs. SHE (SI, Section S8). The only possibility for continued surface reduction is then ultimately determined by the probability that the near-surface H 2 O 2 species re-adsorbs onto Au(111) rather than diffusing into the bulk. This competition may be particularly relevant in the case of roughened Au electrodes, elucidating e.g. the varying ORR selectivity with surface morphology.