Micropore-Dominant Vanadium and Iron Co-Doped MnO2 Hybrid Film Electrodes for High-Performance Supercapacitors

To further improve the electrochemical performance of electrode materials for supercapacitors, we have achieved a significant increase of the micropore volume of a MnO2 hybrid film on IrO2 nano-wedges grown on a pre-treated Ti plate by the co-doping of vanadium and iron (V+Fe). X-ray diffraction and microstructural analyses demonstrate that the V+Fe co-doped MnO2 hybrid films consist of the lamellar structure that is composed of γ-MnO2 nanocrystallites jointed by disordered interface. Nitrogen sorption analysis confirms that the pore characteristics of the MnO2 film change from mesopore-dominant to micropore-dominant after the co-doping, accompanied by increases in the pore volume and specific surface area. The specific capacitance of the V+Fe co-doped MnO2 hybrid film electrode declines from 426 F g−1 to 314 F g−1 with a relatively limited loss of 26% when the galvanostatic (GV) charging-discharging rate is increased from 0.2 to 5 A g−1. In particular, the doped MnO2 film electrode has a loss of only 6% in the specific capacitance after 9000 cycles at a charge-discharge current density of 10 A g−1.