A note regarding the rate-determining step of reduction of solid manganates(V)

Potential pulse chonoamperometry was applied to immobilized microparticles of manganates(V) and MnO2 in order to compare the nature of the rate determining step in their reduction. Manganates(V) were found to be reduced by an irreversible one-electron surface reaction, whereas MnO2 reduction is controlled by a reversible reaction coupled to solid-state diffusion. The key importance of the coordination preferences of reacting metal ions on the surface layer of the solid particles is also discussed with respect to known mechanisms of electrochemical dissolution of Fe and Cr oxides.