The mechanistic picture emerging from Fig. (a) does not show a clearly dominating reaction path at PZC. This is quite unlike the corresponding Fig. (a) and suggests a close competition between protonation to HOOH* and direct OOH* desorption under these conditions. Once again, the initial OOH* state is found in the bottom left part of the plot (black square) at ca. 2.3 Å above Au(111) and ξ + ≈ 0.9. We identify two channels out of this minimum: The first path involves moving predominantly along the y-direction with desorption of a negatively charged HO - 2 species. The corresponding transition state at ca. increasing preference for the peroxide (iii) over the desorption (iv) path with reducing potential. This preference is even more pronounced under working ORR conditions in the lower panel Fig. ). We see here a single, dominating reaction path where OOH* spontaneously protonates to HOOH* (black circle at ca. 3.1 Å height and ξ + ≈ 1.7) and subsequently desorbs as H 2 O 2 with vanishingly small reaction barriers (black triangles). Whether the reaction product will stay in this state in the bulk electrolyte or deprotonate to form HO - 2 will of course be ultimately determined by the electrolyte pH.