Electrochemical properties and capacitance of Hausmannite Mn3O4 - carbon composite synthesized by in situ autocombustion method.

- In-situ autocombustion method is utilized to prepare Mn3O4-carbon composites with uniform distribution of the components
- Optimal performance is demonstrated by 34 wt.%Mn3O4-carbon composite with specific mass capacity of 754 F/g(oxide) at 1 mV/s and 439 F/g at 500 mV/s
- Fast redox transformation of Mn3O4 is suggested to provide main contribution into high pseudo-capacitance at alkaline pH
- As pH decreases from 14 to 10 the contribution of these redox transformations systematically and significantly diminishing

Manganese oxide - carbon composites consisting in Hausmannite Mn3O4 nanoparticles and Vulcan carbon were prepared by in situ autocombustion method (ISAC). The electrochemical properties of the composites and their pseudo-capacitance have been evaluated at different pH. The composites with optimized carbon content demonstrated at pH = 14 high specific oxide capacitance (754 F/g of oxide at 1 mV/s) with just a moderate decrease at higher sweep rate (439 F/g at 500 mV/s). Relatively fast and reversible redox transformations of Mn3O4 into substoichiometric possibly hydrated oxides were tentatively proposed as the main processes responsible for observed pseudo-capacitance. High oxide capacitance suggested that the bulk of oxide particles is participating in charge storage. Systematic decrease of the reversibility and contribution of these redox processes into pseudo-capacitance was detected when pH decreases from 14 to 10. A continuous decrease in capacitance during 10000 galvanostatic cycles was observed at high pH (13 and 14); however, capacitance stabilized at lower pH after a drop during first few thousand cycles.

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