It is already well documented that the thermodynamic stabilization of O2 •-by the acidity of hydrogen bond (HB) donor significantly affects the CV. The CV of O2 in aqueous solutions or in the presence of strong acids in aprotic solvents becomes an irreversible bielectronic CV, where a PT to O2 •-occurs forming hydroperoxyl radical (HO2 • ), resulting in further reduction. Additionally, Evans et al. reported that the CVs of O2/O2 •-in aprotic solvents in the presence of weak acids (HB donors) are characterized by a positive shift in potential, where quasireversible monoelectronic CV without loss of reversibility is kept. Interestingly, the obtained CV of O2/O2 •-in the presence of H2Q demonstrates modifications from quasireversible to irreversible monoelectronic curve demonstrating the O2 •- scavenging by H2Q. This specific CV behavior was observed when a homogeneous PCET involving two PTs and ET occurs between O2 •-and H2Q along the CVs with superior kinetics. We named this mechanism the concerted two-proton-coupled electron transfer (2PCET, Scheme 1), a type of PCET mechanism. Similarly, highly efficient ET of multiprotoncoupled electron transfer observed in HB networks has been previously reported. These studies showed that PCET proceeds efficiently when protons and one electron concertedly move along each orbital in a preformed HB complex, implying that hydroxyl (OH) or amino (NH) protons play a functional role in improving ET efficiency through the PCET mechanism.