Preparations And Electrochemical Applications Of Nickel Based Nanomaterials/Nanocomposites

As one subject studying the conversion principle and process between electrical and chemical energy, electrochemical application technology has been regarded as an important part of national economy. It has been widely used in many aspects of social production, including the development and utilization of new energy systems, the development of electrochemical sensors, the metal finishing, the electrochemical corrosion and protection, the electrolytic synthesis of organic and inorganic compounds.Along with the emergence of nanomaterials and the development of electron microscope, nanomaterials possessing distinct properties with bulk materials attract wide attention and great interest of researchers worldwide. Due to the characteristics of small dimensions and large surface areas, nanomaterials can demonstrate unique properties, including the discontinuity of electronic energy level, quantum size effect, small size effect, surface effect and macroscopic quantum tunneling effect, etc. When applied as electrode materials, nanomaterial will reveal some discontinuous and significant changes in its electrochemical properties as well. For example, the critical current density will increased significantly in the electrode with small size electrode materials. Particularly, nanomaterials have been widely used in the field of Li ion battery, supercapacitor and electrochemical sensor, and some notable achievements have been obtained already. In this thesis, we choose nickel based materials and corresponding composites as object, study the controllable synthesis and electrochemical properties of these materials systematically. The materials have been mainly applied in the devices of supercapacitor, Li ion battery and electrochemical sensors. And the main research content includes the following aspects:(1) Trough a simple hydrothermal process, Ni2(OH)2CO3nanowall arrays can grow on the stainless steel substrate. We analyze and summarize the grow conditions for this kind of nanostructure. By annealing in Ar, Ni2(OH)2CO3can evolve into NiO nanowall network arrays finally. The NiO nanowall arrays on Fe-Co-Ni can be applied as electrode for supercapacitor directly, saving the tedious electrode preparation process. This NiO nanowall arrays demonstrate high specific capacity, superior rate performance and long cycle life in three-electrode system.In order to boost the performances of supercapacitors and get high energy density, we realize the growth of C/CoNi3O4hierarchical network arrays on stainless substrate by a simple and template-free two-step method. The C/CoNi3O4nanocomposite possess intriguing structure with nanowires growing uniformly on the nanowalls, meanwhile, the nanowalls connect with each other to form a network. After glucose coating and annealing in Ar process, large quantity of mesopores appeared in the nanowalls and nanowires due to the loss of CO2and H2O during the annealing process, leading to a large surface area of128.1m2/g. This C/CONi3O4nanowall arrays grow intimately on the conductive substrate as well and can be applied directly as electrode for supercapacitors. In both two-electrode and three-electrode system, this C/CoNi3O4nanocomposite demonstrate excellent electrochemical properties, considering its enhanced specific capacity, superior rate performance and long cycle performance. These results provide strong evidence for that nickel based materials are one kind of promising electrode materials for the practical application of supercapacitors.(2) Adopting the Ni2(OH)2CO3nanowall arrays as substrate, through a one-step hydrothermal process we can obtain the3-dimensional (3D) Ni2(OH)2CO3/SnO2nanocomposite arrays. The Ni2(OH)2CO3nanowalls connect with each other to form a network structure and SnO2nanorods .grow uniformly on each nanowall, resulting the hierarchical network architecture. Through the process of glucose coating and annealing-reduction, the final product of Ni/SnOx/C can be obtained. The final product of Ni/SnO,/C remain the3D network structure, carbon coated SnOx nanorods grow uniformly on the metallic Ni nanowalls to form a network architecture. When applied as anode materials for Li ion microbatteries, this Ni/SnOx/C nanocomposite reveal high areal capacity, superior rate performance and enhanced cyclic performance, demonstrating much better performances than the pure SnOx nanorod electrode.Through the hydrothermal process, we can successfully encapsulate transitional metal oxides (including ultralong MnO2nanowires and CoO nanowire arrays on Ti foil) in the ultra-thin Ni(OH)2lamellas. After conducting heat treatment towards MnO2@Ni(OH)2and CoO@Ni(OH)2in a mild reducing atmosphere, we can get the final products of MnO@Ni nanowires and CoO@Ni nanoarrays. When applied as anode materials, both of the composites demonstrate superior electrochemical performance, with higher capacitance, superior rate performance and enhanced cycle performance. Compared with the pure MnO and CoO electrode, the performances are largely improved with the metallic Ni coating layer, bring forth strong evidence for the fact that Ni coating can enhance the electrode performance. Besides, we also put forward one simple and general method for the preparation of3D metallic network shell with metal oxide core structrue, which play a positive role in promoting the development of LIB electrode materials.(3) Adopting Ni2(OH)2CO3nanowall arrays as precursor, after conducting heat treatment towards precursor in light-reducing atmosphere, we can get the final product of CNTs/Ni nanocomposite arrays. Just like the Ni2(OH)2CO3nanowall arrays, the CNTs/Ni nanocomposite retain the interconnected nanowall arrays structure, moreover, curved multiwall CNTs distributed on the surface of nanowalls uniformly. Growing on the conductive substrate, this CNTs/Ni nanocomposite can be used directly as electrode for nonenzymatic glucose sensors. And the CNT/Ni electrode reveal superior electrochemical performances, with low detection limitation, wide detection line range and high sensitivity. Moreover, other excellent properties of the CNTs/Ni nanowall arrays electrode, such as good reproducibility, long-term stability and anti-interferences, are demonstrated as well. The good analytical capability, low cost and facile preparation method make CNT/Ni nanowall arrays promising for amperometric non-enzymatic glucose detection.