HO2 -+ H + → H2O2 the second PT (5) Based on these results, we rationalized that O2 •-formed after the primary electrode process associated with PT from OH, leading to the irreversible overall reduction of O2 to H2O2 driven by the exergonic ET (homogeneous ET or heterogeneous-electrode reduction) of the resulting HO2 • /HO2 -. Therefore, the CV traces of O2/O2 •-in the presence of phenolic compounds (Figure (a-e)) were divided into two typical curves: type A depicting the irreversible one-electron process (Equations ( ), ( ), ( ) and ( )) leading to O2 •-scavenging, and type B depicting the irreversible two-electron process observed in electro-chemical-electro reactions (Equations ( )-