Furthermore, Ni foam also provides a highly conductive network for electron transport during the charge and discharge processes. The endurance test was conducted using galvanostatic charging-discharging cycles at 1 A · g-1 (insert of Figure 4d). The discharge capacitance loss after 2,000 consecutive cycles is about
20%. The specific capacitance degradation is estimated to be from 263 to 205 F · g-1 (Figure 4d). Although the Ni foam serves as a conductive matrix to promote fast Faradaic charging and discharging of the Mn3O4 nanorods, its loose structure leads to the flaking off of the nanorods from the Ni foam substrate. Time-dependent INCB28060 molecular weight Mn3O4/Ni foam composite properties To shed light on the formation process, temporal evolution of the Mn3O4 nanostructures was studied by examining the GSK2245840 nmr products obtained under different reaction times of 1, 4, and 8 h. XRD patterns and Raman spectra selleckchem were measured to identify the components of the different samples. The XRD patterns of the composite obtained under 1 h can be indexed to MnO2 and Mn3O4 crystal structures (Figure 5a). For the composites obtained under 4 and 8 h, the intense XRD peak at 2θ ≈ 19°disappeared corresponding to the MnO2 (200) crystal structures and the left peaks attribute to the Mn3O4 crystal structures. Figure 5b shows the Raman spectra of the powder scratched from composite electrodes. The peak position of composites
obtained under 4 and 8 h are red shifted compared with that of the composite obtained under 1 h. As is known, the Raman spectra for the MnO2 PI-1840 phase and the Mn3O4 phase are located at 638.5 cm-1 and 652.5 cm-1, respectively . Therefore, this red shift of Raman spectra indicates the component variation from the MnO2 phase to Mn3O4, which is in excellent agreement with the result obtained from the XRD study. The SEM images of products obtained under different reaction times of 1, 4, and 8 h are shown in Figure 6. The products collected after 1 h consisted of nanosheets with a thickness of about 30 nm (Figure 6a,b). When the reaction
time increases to 4 h, some nanorods accompanied with nanoparticles begin to appear (Figure 6c,d). As the reaction proceeds to 8 h, the nanosheets disappeared and all of the products are nanorods with few nanoparticles (Figure 6e,f). After 10 h of the hydrothermal reaction, well-defined nanorods are obtained (Figure 3c,d). Based on the time-dependent morphology evolution described above, the formation mechanism of Mn3O4 nanorods can be proposed. At the initial stage, a large number of nanocrystallites nucleate and grow into nanosheets to minimize the overall energy of the system. However, the nanosheets are just intermediate products and not stable. After the reaction for 4 h, some of the nanosheets dissolve with the emergence of nanorods with some nanoparticles. When the reaction proceeds for 8 h, all of the nanosheets have transformed into nanorods with nanoparticles.