Nanoflake manganese oxide and nickel-manganese oxide synthesized by electrodeposition for electrochemical capacitor

Nanoflake structures of electrochemical manganese oxide (EMD) and nickel mixed manganese oxide (NiMD) were directly deposited on a stainless steel by using Chronoamperometry and Cyclic Voltammetry (CV) techniques. The structure, morphology, and capacitive behavior of EMD or NIMD nanoflake were affected by the electrodeposition modes and deposition time. The highest specific capacitance (C sp) was obtained for only two-minute deposition by both methods. EMD nanoflakes electrodeposited by CV technique show higher specific capacitance values than those prepared by Chronoamperometry owing to its homogenous and highly porous surface. All EMD samples exhibited excellent cycle behavior, less than 5% capacitance loss after 1000 cycles. Ni mixed MnO2 was prepared at different Mn²⁺/Ni²⁺ ratios for 2 minutes of electrodeposition. The presence of Ni²⁺ ion enhanced the C sp value at high charge-discharge rate due to the decrease of the charge transfer resistance. The supercapacitor prototype of 2 cm × 2 cm was assembled using EMD and NiMD as electrode material and tested at 1 A·g^-1.