Manganese oxidation, free energy

Manganese(III,IV) oxides are reduced by phenolic compounds an order of magnitude more quickly than Co(III) oxides, and several orders of magnitude more quickly than Fe(III) oxides. This apparent relationship between reaction-free energy and reaction rate is not likely to arise from differences in adsorption phenomena alone. Instead, it probably arises from differences in electron-transfer rate within the surface precursor complex. 

Oxidation-reduction reactions involving iron and manganese include changes in oxidation states, relative stabilities of iron and manganese compounds, and the energetics and kinetics of oxidized and reduced compounds. Using thermodynamic data (from free energies of formation, see Chapter 4),... 

These examples show that oxidizing carbon at the expense of reducing manganese and even more so iron gives relatively little free energy, 22-335 kj per each carbon atom. 

Perera, S. D., M. Rudolph, R. G. Mariano et al. 2013. Manganese oxide nanorod-graphene/vanadium oxide nanowire-graphene binder-free paper electrodes for metal oxide hybrid supercapacitors. Nano Energy 2 966-975. 

---