Insights into the surface-defect dependence of molecular oxygen activation over birnessite-type MnO2

•There are 3 times faster degradation rate, 11 KJ/mol reduced activation energy and ∼30% degradation content of (100) MnO2 than that of (001) MnO2.•EPR detected superoxide radical (O2−) and hydroxyls (OH−) on (001) MnO2 and peroxide radical (O22−) on (100) MnO2.•Superoxide species was identified with OO bond length of 1.23 Å and peroxide species with OO bond length of 1.44 Å by DFT calculation.