Influence of surfactant on the capacitive performance of manganese dioxide prepared at different temperatures

MnO2 electrode materials is prepared by co-precipitation at different preparation temperatures in the presence of surfactant cetyl trimethyl ammonium bromide (CTAB). The as-prepared MnO2 are characterized systematically by a variety of means such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and nitrogen adsorption. Results show that, with the rise of preparation temperature, the crystalline phase of MnO2 changes from a single α-MnO2 into a mixture of α-MnO2 and γ-MnO2, the crystal size becomes larger, the mesopore volume and specific surface area decrease. As evidenced by cyclic voltammetry and galvanostatic charge/discharge measurements, the capacitive performance of the samples prepared at low temperatures is better than those prepared at high temperatures. The specific surface area and specific capacitance of sample prepared at 5 °C are 223 m2 g−1 and 170.8 F g−1, respectively. It is indicated that, at the temperature lower than Krafft point, CTAB monomer has better dispersion effect on manganese dioxide particles compared with its micelle. The presence of CTAB monomer can suppress the reunion of particles and improve the capacitive performance of MnO2.