Ca 2+ ‐Induced Oxygen Generation by FeO 4 2− at pH 9 – 10

Although FeO 4 2− (ferrate(IV)) is a very strong oxidant that readily oxidizes water in acidic medium, at pH 9–10 it is relatively stable (<2 % decomposition after 1 h at 298 K). However, FeO 4 2− is readily activated by Ca 2+ at pH 9–10 to generate O 2 . The reaction has the following rate law: d[O 2 ]/d t = k Ca [Ca 2+ ][FeO 4 2− ] 2 . 18 O‐labeling experiments show that both O atoms in O 2 come from FeO 4 2− . These results together with DFT calculations suggest that the function of Ca 2+ is to facilitate O–O coupling between two FeO 4 2‐ ions by bridging them together. Similar activating effects are also observed with Mg 2+ and Sr 2+ .