Effect of Buffer Layer Capacitance on the Electrical Characteristics of Ferroelectric Polymer Capacitors and Field Effect Transistors

Synthesis of flower-like MnO2 nanostructure with freshly prepared Cu particles and electrochemical performance in supercapacitors

Four types of flowerlike manganese dioxide in nano scale was synthesized via a liquid phase method in KMnO₄-H₂SO₄ solution and Cu particles, wherein the effect of Cu particles was investigated in detail. The obtained manganese dioxide powder was characterized by XRD, SEM and TEM, and the supercapacity properties of MnO₂ electrode materials were measured. The results showed that doping carbon black can benefit to better dispersion of copper particles, resulting in generated smaller size of Cu particles, and the morphology of MnO₂ nanoparticles was dominated by that of Cu particles. The study of MnO₂ synthesis by different sources of Cu particles showed that the size of MnO₂ particles decreased significantly with freshly prepared fine copper powder compared with using commercial Cu powder, and the size of MnO₂ particles can be further reduced to 120 nm by prepared Cu particles with smaller size. Therefore, it was suggested that the copper particles served as not only the reductant and but also the nuclei centre for the growth of MnO₂ particles in synthesis process MnO₂, and that is the reason how copper particles worked on the growth of flower-like MnO₂ and electrochemical property. In the part of investigation for electrochemical property, the calculated results of b values indicated that the electrode materials have pseudo capacitance property, and the highest specific capacitance of 197.2 F g^-1 at 2 mV s^-1 and 148 F/g at 1 A/g were obtained for MCE electrode materials (MnO₂ was synthesized with freshly prepared copper particles, where carbon black was used and dispersed in ethanol before preparation of Cu particles). The values of charge transfer resistance in all types of MnO₂ materials electrodes were smaller than 0.08 Ω. The cycling retention of MCE material electrode is still kept as 93.8% after 1000 cycles.