Stepwise Reduction of Oxygen +2e,2H+ teH +e,H+ +e,H+ +e.H+ O2—*HOO.—HOOH+HO+OH=·2HOH H++o H++OoH H++·O pKa 4.8 11.8 11.9 South China University of TechnologySouth China University of Technology O2 HOO· HOOH HO·+-OH 2HOH +e - ,H+ +e - ,H+ +e - ,H+ +e - ,H+ +2e - ,2H+ Stepwise Reduction of Oxygen H++·O2 - pKa 4.8 H++ -OOH 11.8 H++·O- 11.9