Effect of chitosan addition on the structure and capacitive characteristics of electrodeposited manganese oxides

Nano-structured MnO2-chitosan hybrid composite electrodes containing low and high chitosan's Mw were synthesized by one-step cathodic electrodeposition on nickel foam substrate for electrochemical capacitors (ECs) application. The effect of chitosan molecular weight (Mw) on the structure and capacitive behaviour of the tailored electrodes was examined. The electrodes have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The presence of CH promotes both ion and electron transport in the matrix of MnO2. Furthermore, the use of CH with its inherent binding properties allowed the formation of adherent and cracks free deposits. The MnO2-chitosan hybrid nanocomposite electrodes showed better specific capacitance and rate capability than MnO2 electrode. The highest specific capacitance of 424 F/g was obtained for the MnO2-chitosan composite electrode with low chitosan's Mw at a current density of 1 mA/cm2. The electrode retained a very stable capacitance over 400 cycles by charging and discharging at 3 mA/cm2, as the capacity loss is only 3%, indicative of long term electrochemical cycling stability.