Preparation And Property Research Of RuO₂·nH₂O-based Nanomaterials By Ion Diffusion Methods

As a typical pseudocapacitive electrode material, ruthenium oxide materials have good electrical conductivity, high reversible electrochemical reaction, longer cycle life, and high specific capacitance, whose CV curve in H2SO4 electrolyte is similar to carbon materials. In addition, compared with carbon materials and conductive polymers materials, ruthenium oxide materials own larger energy storage and specific capacity and longer cycle life. Therefore, the study of amorphous and crystalline RuO2 becomes the most core for supercapacitive electrode materials from the beginning 1970s. And because of the high cost of ruthenium, the research of ruthenium oxide based composites garners increasing attention recently.In this thesis, A novel inorganic synthesis method i.e. ion diffusion controlled by ion exchange membrane was used for synthesizing RuO2·nH2O nanomaterials and GO/ RuO2·nH2O composites. To understand the morphology, structure, formation process and relative performance of ruthenium oxide and its composites, there are various kinds of characterization technologies applied in this study. The details are as follow:(1) RuO2·nH2O nanoparticles were prepared directly in deionized water solutionby ion diffusion method. It was found that the structure of RuO2·nH2O nanoparticles is closely related to annealing temperature, which will lead to different supercapacitor performance.The morphology, structure and composition of the samples are characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TG-DTA) and X-ray photoelectron spectroscopy spectrum (XPS). The results show that amorphous RuO2·nH2O prepared by the ion diffusion method transforms into the crystalline one, the grain size becomes larger and the specific area decreasing with increasing annealing temperature. The data of cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy show that an appropriate annealing temperature is vital to obtain nanoparticles RuO2·nH2O with suitable electrochemical behavior. The results indicate that RuO2·nH2O annealed at ca.150℃ exhibits a maximum specific capacitance, which can reach 673.37 F/g in 1.0 M H2SO4 electrolyte at a scan rate of 2 mV/s.(2) RuO2·nH2O nanoparticles were prepared with CTAB and some anionic surfactants by the ion diffusion method, to optimize the morphology and degree of dispersion. The morphology, structure and composition of the samples with surfactants are characterized by using SEM, TEM, XRD and EDX technologies. The data show that there is no apparent change in morphology of RuO2·nH2O nanoparticles with surfactants except that the size of the particles and the specific capacitance become smaller than before, especially with 1.0 g/L copolymerization of methyl zcrylate and styrene sodium salt (DS36). However, the specific capacitance of RuO2·nH2O nanoparticles with 1.0 g/L DS36 is a litter higher than the single RuO2·nH2O annealed at 450℃ under the same conditions.(3) GO/RuO2-nH2O nanocomposites were prepared by ion diffusion method at room temperature in graphene oxide (GO) solution. The morphology, structure and composition of the composites are characterized by using SEM, TEM, XRD and XPS technologies. In this work, we discussed the supercapacitor performances of nanocomposite with different mass ratios. It was found that with mass ratio of GO increasing, the degree of dispersion becomes better and the size of GO/RuO2·nH2O nanocomposite is ca.15 nm. In addition, nanocomposites GO/RuO2·nH2O with 0.01 g/L GO exhibits a maximum specific capacitance, which can reach 549.77 F/g, which is generally better than that of the single nanoparticles under the same conditions.