Improvement of hydrothermally synthesized MnO2 electrodes on Ni foams via facile annealing for supercapacitor applications
Nanostructured manganese dioxide (MnO2) is deposited on nickel foams by a hydrothermal synthesis route. As-deposited MnO2 thin films are largely amorphous. Facile post-deposition annealing significantly improves the electrochemical performance of the MnO2 thin films via changing their morphology, phase, and crystallinity. The specific capacitance of the MnO2 electrode increases with the annealing temperature and reaches an optimal value of 244 F g−1 (at the current density of 1 A g−1) in a neutral 1 M Na2SO4 electrolyte for a specimen annealed at 500 °C. Furthermore, when an alkaline 5 M KOH electrolyte is used, an exceptionally high capacitance of 950 F g−1 is achieved at the current density of 2 A g−1. The cost-effective facile synthesis, high specific capacitance, and good cycle stability of these MnO2-based electrodes enable their applications in high-performance supercapacitors.
KeywordsMnO2 Specific Capacitance Hydrothermal Synthesis Cyclic Voltammetry Curve Manganese Dioxide
This study is primarily supported by Shanghai Pujiang Program under Grant No. 11PJ1403400. J. Luo acknowledges an NSF Grant No. DMR-1320615 for supporting his research in the area of oxides/ceramics for energy storage and a National Natural Science Foundation of China Grant No. 51228202 for partially supporting his travel to Shanghai to conduct collaborative research. The authors thank the support from the Instrumental Analysis and Research Center of Shanghai University and GE (China) Research and Development Center Co., Ltd.