Cathodic electrodeposition of MnOx films for electrochemical supercapacitors

Cathodic electrosynthesis has been utilized for the fabrication of MnOx films. The use of polyethylenimine (PEI) as an additive enabled the formation of adherent films, which exhibited enhanced resistance to cracking during drying. The polymer content in the deposits can be varied by the variation of the polymer concentration in the solutions. The mechanism of PEI deposition was proposed which is based on the use of PEI–Mn2+ complexes. The deposition yield has been studied at different deposition durations. X-ray diffraction analysis showed the crystallization of Mn3O4 phase at 300 °C and Mn2O3 at 500 °C. The electrochemical performance of the MnOx films sintered at different temperatures was studied by cyclic voltammetry (CV), chronopotentiometry and impedance spectroscopy in Na2SO4 solutions. The films showed excellent pseudocapacitive behavior. The specific capacitance (SC) of 425 F/g in a potential window of 0–0.9 V was obtained from the CV data at a scan rate of 10 mV/s. The SC calculated from the chronopotentiometry data is about 445 F/g. The SC decreased by ∼20% after 1000 cycles. SEM investigations revealed changes in the film morphology during cycling. Obtained results indicate that the proposed method can be used for the fabrication of electrodes for electrochemical supercapacitors.