Novel promising aqueous electrolytes for manganese dioxide/stainless steel pseudocapacitor electrode

Abstract Manganese dioxide (MnO 2 ) films are developed by potentiostatic electrodeposition on a stainless steel sheet as a current collector using manganese acetate tetrahydrate solution at a concentration of 0.25 mol L −1 . The deposited sample layer is found to be amorphous as confirmed by the scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses. The capacitive property of the prepared electrodes is characterized by charging/discharging, cyclic voltammetry, and electrochemical impedance spectroscopy techniques in four different aqueous solutions; sodium sulfate, magnesium acetate, nickel acetate, and a mixture of sodium chloride + sodium bicarbonate + borax. Charge–discharge curves reveal higher specific capacitance ( C s ) of 1580 F g −1 at 0.5 mA cm −2 for the investigated MnO 2 film which is characterized in Ni acetate aqueous solution. The structural, morphological, and electrochemical properties of the electrodeposited manganese oxide films are also studied. The results indicate that the specific capacitance of the deposited samples showed a strong dependency on the electrolyte aqueous solutions, resulting in developing new electrolytes which is a top priority effort in comparison to seeking new electrode materials. It is found that the matching between the pore size structure of the electrode and the ion size of the electrolyte is of great importance for the improved capacity of prepared capacitors.