Study On Graphene-Based Composites For Electrochemical Sensors And Supercapacitors

Graphene with a unique structure and many excellent properties, as the most ideal two-dimensional nanomaterial by far, has caused the research upsurge in the world since be found. The two-dimensional structure of graphene is very suitable for loading different nanomaterials, and its excellent conductivity can improve the electrical conductivity of the material. Multi-component composite materials can play to the advantages of various components, realize the synergistic effect between different materials and remedy the limitation that a single material can not meet the demand of various aspects performance. Various methods are used to synthesize graphene-based composite materials. Among those, the electrochemical method has advantages of low cost, easy operation and high product purity, can also grow on the surface of different substrates directly.In this thesis, simple electrochemical method was used to synthesize graphene thin film with high electrochemical activity on the surface of nickel foam. The graphene/Co(OH)2 nanocomposite material and graphene/Mn2O3 nanocomposite material with excellent electrochemical performance were further prepared through electrochemical approach. And the application in electrochemical sensors and supercapacitors was researched. The main results of the research are as follows:1. The graphene/Co(OH)2 nanocomposite was prepared by two-step method of electrodeposition. Scanning electron microscope (SEM), Raman spectroscopy and X-ray diffraction (XRD) were used to prove its structure and composition. As a electrode material in supercapacitors, the Ac impendance test had shown that the addition of graphene improved the conductivity of the Co(OH)2 nanoflakes. The electrode material had a specific capacity of 857.1 F g-1 at the current density of 2 A g-1, and had a good good cycling stability.2. The obtained graphene/Co(OH)2 nanocomposite was applied in enzymeless glucose detection research. The results had shown that graphene/Co(OH)2 nanocomposite could detect glucose with a ultrahigh sensitivity and a remarkable lower detection limit of 0.1 μM (S/N-5). And the electrode with good selectivity and long-term stability, was expected to the application in the enzymeless glucose detection of the actual samples.3. The graphene/Mn2O3 nanocomposite was synthesized rapidly by the electrochemical method. The results of scanning electron microscope (SEM), X-ray diffraction (XRD) characterization had shown that three-dimensional porous Mn2O3 nanoflakes were uniformly loaded on the graphene film. The cyclic voltammograms tests had shown that compared with single materials, the electrochemical performance of graphene/Mn2O3 nanocomposite had an obvious improvement, this was the result of two kinds of material synergy effect. The graphene/Mn2O3 nanocomposite material had a specific capacity of 114.3 F g"1 at the current density of 1 A g"1 in the charge and discharge tests and was potential in the application in supercapacltors.