Effect of iron particle addition on the pseudocapacitive performance of sol–gel derived manganese oxides film

Manganese oxide electrodes with promising behavior were prepared successfully by sol–gel process. Manganese oxide films were also modified with the addition of submicron-crystalline iron powders. Effects of post heat treatment and iron submicron-powder addition on the material characteristics and electrochemical capacitance of the manganese oxide electrodes were investigated. The experimental results showed that manganese oxide films composed from metal-organic precursors at 250 °C heat treatment, while formation of MnO2, Mn2O3, Mn3O4, Fe2O3, and Fe3O4 phases were observed after heat treatment at a temperature higher than 300 °C. The specific capacitances were 48.9, 140.1, 212.7, and 81.1 F g−1 for manganese oxide films heat treated at 250, 300, 350, and 400 °C, respectively. The specific capacitances were 75.7, 227.3, 247.9, and 152.9 F g−1 for manganese/iron oxide films (Mn:Fe = 100:1) heat treated at 250, 300, 350, and 400 °C, respectively. The manganese/iron oxide films (Mn:Fe = 100:1) treated at 350 °C exhibited the highest specific capacitance 247.9 F g−1 of the electrodes investigated in the present study. After 1000 cyclic voltammetry tests, the specific capacitance decreased by only 10 percent. The surface morphology of this film exhibited powders with linked nano-sized particles. The number of special particles reached a maximum after heat treatment at 350 °C. The experimental results showed that post heat treatment and iron submicron-particle addition may change the surface morphology and structure, increase the specific capacitance, and improve the electrochemical performances of the manganese oxide electrodes.