Synthesis, chracterization and pseudo-capacitive performance of MnO x/CNT heteronanostructures

Abstract

Manganese oxide based nanoparticles were synthesized by sol-gel process. Methanol, propanol and methanol+propanol were used as alternative solvent during sol-gel process with manganese acetate as precursor for the preparation of pristine manganese oxide. Hybrid MnOx modified by additions of carbon nanotubes was further prepared. The mean particle sizes ranged between 9 and 15 nm. XRD results showed that the as prepared manganese oxide based samples at calcination temperature of 300°C and above were composed of Mn 2O3 as dominant phase, with Mn3O4 as minor phase. Specific capacitance measured from two electrode systems of manganese oxide prepared from methanol, propanol and methanol+propanol at scan rate of 10 mV/s were 80.9, 104.8, 331.7 F/g and the result for the hybrid sample prepared in methanol was 140.5 F/g. Manganese oxide nanofibers prepared by electrospinning method yielded a specific capacitance of 161.22 F/g at a scan rate of 10 mV/s. The hybrid MnOx/CNT nanofibers showed only a negligible improvement in specific capacitance to 182.2 F/g. However, the MnOx with 1% SnO2 nanofibers showed a tremendous improvement in the specific capacitance. The MnOx/SnO2 nanofibers exhibited a capacitance of 472.31 F/g. While the above analysis was carried out in a 2 electrode button cell, additional characterization in a 3-electrode cell showed that the observed capacitances are significantly higher than the 2-electrode cells. For example the MnOx and MnOx/CNT cyclic voltammetry conducted in a 3 electrode cell showed specific capacitances of 299.14 F/g and 349.53 F/g, respectively.