Electrochemical capacitance of MnOx films

Cathodic electrosynthesis has been utilized for the fabrication of nanostructured MnOx films, containing chitosan additive as a binder. The films were studied by differential thermal analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy, X-ray diffraction analysis and scanning electron microscopy. Cyclic voltammetry (CV) and chronopotentiometry data for the films tested in 0.1 M Na2SO4 solutions showed high specific capacitance (SC) in the voltage window of 0–0.9 V versus SCE. The capacitive properties of the films were enhanced within the first few cycles of testing. SEM investigations revealed changes in the film morphology during initial cycling. The highest SC of ∼400 F g−1 was obtained for a film of mass 50 μg cm−2 heat-treated at 300 °C at a CV scan rate of 5 mV s−1. The SC decreased with increasing film mass and scan rate. Ragone plots indicated that the obtained films possessed good power–energy density characteristics, with a highest power density of 45 kW kg−1 for the 50 μg cm−2 MnOx film. Excellent cycling behavior was observed for the films, with no loss in SC during 1000 cycles.