Rapid microwave-assisted solid-state obtention of Mn3O4 and its electrochemical characterization for application as supercapacitor electrodes

A rapid and facile microwave-assisted method coupled with a mild mechanical treatment is proposed to obtain Mn3O4 with good properties to be used as a supercapacitor material. Mn3O4 was produced by thermal decomposition of epsilon-MnO2 using microwave irradiation in a practical setup and a domestic microwave oven. XRD results, supported by other physical characterizations such as TG/DTA and FTIR and Raman spectroscopy analyses, attested that Mn3O4 was obtained as a single phase after only 5 min of microwave heating. After submitting an oxide sample to a mild mechanical treatment in an adapted ball-mill setup for 30 min, SEM micrographs and BET analyses revealed a particle size in the range of 200-600 nm and a fivefold increase of the specific surface area. The pseudocapacitive behavior of electrodes prepared with the thus obtained Mn3O4 was analyzed by cyclic voltammetry in a 0.1 mol L-1 Na2SO4 aqueous solution. Galvanostatic charge and discharge tests of these electrodes were performed in the 1.0 to 5.0 A g(-1) range in the same electrolyte; at 1.0 A g(-1), they presented an initial specific capacitance of about 160 F g(-1) and good electrochemical stability up to 5000 cycles.