Manganese Dioxide Polymorphs As Oxygen Reduction Catalysts

Oxygen, a chemically reactive element, is consumed during the oxygen reduction reaction (ORR) via a cathodic reduction process in almost all fuel cell systems. Electrochemical reactions involving oxygen are kinetically slow, therefore, electrocatalysts are needed to increase the rate of this reaction. The ORR activity of electrodeposited manganese dioxide, as well as different powdered polymorphs of MnO₂ (α-MnO₂; β-MnO₂; γ- MnO₂ ; δ-MnO₂; λ- MnO₂) has been investigated using a glassy carbon substrate.  Dimethyl sulfoxide (DMSO), dimethylformamide (DMF) and acetonitrile (ACN) with tetraethyl ammonium tetra fluoroborate was used as a supporting electrolyte to assess activity using rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) measurements. The results and the effects of different polymorphs will be described and discussed. Overall, the polymorphs of MnO₂ catalysts exhibit good catalytic activity.