However, O2 peaks (pc1, E ⸰ O2) and the prepeak: O2-mH2Q (pc3, E'O2) are observed separately in Figure . This CV behavior was attributed to a lack of concentration of the HB complex (O2-mH2Q) at the electrode surface along the cathodic potential sweep. Although the complexation processes (vertical processes in Figure ) are fast and reversible, [O2-mH2Q] depletes, possibly because the subsequent reaction (2PCET) is irreversible. Therefore, Equation ( ) is inappropriate to represent the CV (Figure ), and the two redox reactions in the equilibrium scheme (horizontal lines) must be defined separately using Equations ( ) and (10).