Fig. 4: Diagram of I-PCET mechanism controlling the activation of O–O bond initiated by a solid-water interface.

A Oxidation of PhOH to PhO·, which involves the abstraction of H^• from PhOH by the electrophilic Cu^III, accompanied by the reduction of Cu^III to Cu^II. B Formation of Cu^III from Cu^II through heterolytic O–O bond activation, where the molar ratio of transferred electrons to coupled protons is close to 1:1, as shown in this study. This indicates that the interfacial O–H bond is directly involved in the oxidation of Cu^II to Cu^III, and the O–H bond is simultaneously broken in response to the temporary removal of an electron from Cu^II to Cu^III.