Facile Low-temperature Chemical Synthesis and Characterization of a Manganese Oxide/multi-walled Carbon Nanotube Composite for Supercapacitor Applications

Mn3O4/multi-walled carbon nanotube (MWCNT) composites are prepared by chemically synthesizing Mn3O4 nanoparticles on a MWCNT film at room temperature. Structural and morphological characterization has been carried out using X-ray diffraction (XRD) and scanning and transmission electron microscopies (SEM and TEM). These reveal that polycrystalline Mn3O4 nanoparticles, with sizes of about 10-20 nm, aggregate to form larger nanoparticles (50-200 nm), and the Mn3O4 nanoparticles are attached inhomogeneously on MWCNTs. The electrochemical behavior of the composites is analyzed by cyclic voltammetry experiment. The Mn3O4/ MWCNT composite exhibits a specific capacitance of 257 Fg �1 at a scan rate of 5 mVs �1 , which is about 3.5 times higher than that of the pure Mn3O4. Cycle-life tests show that the specific capacitance of the Mn3O4/ MWCNT composite is stable up to 1000 cycles with about 85% capacitance retention, which is better than the pure Mn3O4 electrode. The improved supercapacitive performance of the Mn3O4/MWCNT composite electrode can be attributed to the synergistic effects of the Mn3O4 nanoparticles and the MWCNTs, which arises not only from the combination of pseudocapacitance from Mn3O4 nanoparticles and electric double layer capacitance from the MWCNTs but also from the increased surface area, pore volume and conducting property of the MWCNT network.