Experiments were conducted using two Mn oxide minerals that differ in the Mn oxidation states (K-birnessite, δ-MnO2 ; (K + )x(Mn III Mn IV )O2 •y(H2O)) and hausmannite ( (Mn II Mn III 2O4). K-birnessite and hausmannite were synthesized as previously described with some modifications. Briefly, the synthesis of K-birnessite and hausmannite involves adding 2 M and 1 M KOH (Alfa Aesar, ≥ 99.98%) solutions to a 0.2 M MnCl2⸱4H2O (Alfa Aesar, ≥ 99.99%) solution at room temperature, and vigorously stirring with O2 (flow ≈ 1.2 L min -1 ) or without oxygenation, for ≈5hr, respectively. The precipitates were centrifuged and washed with DI water (18.2 MΩ‧cm) to reach an electrical conductivity below 20 μS cm -1 . The purified pellets are then freeze-dried and stored in N2-purged containers at 5 C° for further experiments. XRD diffractograms, TEM images, and physicochemical properties of synthesized Mn oxides are shown in Figure and Table , Supplementary Information (SI).