Surface activation of electrocatalysis at oxide electrodes. Concerted electron-proton transfer.

Dramatic rate enhancements are observed for the oxidation of phenols, including tyrosine, at indium-tin oxide electrodes modified by the addition of the electron-transfer relays [M(II)(bpy)(2)(4,4'-(HO)(2)P(O)CH(2))(2)bpy)](2+) (M = Ru, Os) with clear evidence for the importance of proton-coupled electron transfer and concerted electron-proton transfer.