Table 1.
Sample composition, average manganese oxidation state, and surface area
| Compositiona | Manganese average oxidation stateb,c | BET surface area, m2/g; and molar surface area, m2/mol |
| Ca0.39⋅Mn(3+)0.21⋅Mn(4+)0.79⋅O2.29⋅0.60H2Od | 3.79 ± 0.01 | 96.97 ± 0.56 |
| 11,461.0 ± 88.1 | ||
| Ca0.39⋅Mn(3+)0.13⋅Mn(4+)0.87⋅O2.33⋅0.48H2Od | 3.86 ± 0.01 | 88.38 ± 0.39 |
| 10,309.4 ± 79.9 | ||
| Ca0.39⋅Mn(3+)0.09⋅Mn(4+)0.91⋅O2.35⋅0.43H2Od | 3.91 ± 0.01 | 71.58 ± 0.36 |
| 8,313.7 ± 65.3 | ||
| Ca0.39⋅Mn(3+)0.06⋅Mn(4+)0.94⋅O2.37⋅0.30H2Od | 3.94 ± 0.01 | 56.64 ± 0.34 |
| 6,456.3 ± 51.8 | ||
| Ca0.39⋅Mn(3+)0.05⋅Mn(4+)0.95⋅O2.37⋅0.28H2Od | 3.95 ± 0.01 | 35.88 ± 0.29 |
| 4,081.0 ± 34.6 | ||
| Ca0.43⋅Mn(3+)0.37⋅Mn(4+)0.63⋅O2.24⋅0.43H2Oe | 3.63 ± 0.01 | 72.84 ± 0.39 |
| 8,426.5 ± 66.0 | ||
| Ca0.43⋅Mn(3+)0.39⋅Mn(4+)0.61⋅O2.23⋅0.42H2Oe | 3.61 ± 0.01 | 63.15 ± 0.34 |
| 7,287.0 ± 59.9 | ||
| Ca0.43⋅Mn(3+)0.28⋅Mn(4+)0.72⋅O2.29⋅0.35H2Oe | 3.72 ± 0.01 | 55.49 ± 0.22 |
| 6,380.9 ± 48.0 | ||
| Ca0.43⋅Mn(3+)0.29⋅Mn(4+)0.71⋅O2.28⋅0.22H2Oe | 3.71 ± 0.01 | 42.35 ± 0.32 |
| 4,768.3 ± 36.1 | ||
| Ca0.43⋅Mn(3+)0.28⋅Mn(4+)0.72⋅O2.29⋅0.15H2Oe | 3.72 ± 0.01 | 35.47 ± 0.29 |
| 3,951.1 ± 28.5 |
a
Sample compositions are normalized to 1 mol of manganese.
b
Details on the Murray titration method (41), along with calculation of manganese AOS and speciation, are provided in SI Tex. Quality control was run between different samples of CaMnO using a reference standard of manganese dioxide (Sigma–Aldrich).
c
Error in the manganese oxidation state titration is the standard error calculated from triplicate titrations.
d
CaMnO sample contains 43.06 ± 0.01 wt% manganese (0.784 mol) and 12.40 ± 0.01 wt% calcium (0.309 mol).
e
CaMnO sample contains 49.00 ± 0.01 wt% manganese (0.892 mol) and 15.28 ± 0.01 wt% calcium (0.381 mol).