Study On Synthesis, Characterization And Properties Of Nanostructured Ni（OH）₂and NiO

As the important P-type semiconductor materials, nanostructured Ni(OH)2and NiO with a large surface area, fast proliferation of protons and perfect electrochemical activity make them show great potential applications in the field of supercapacitors, gas sensor, catalysts and so on.In this paper, the Ni(OH)2and NiO nanosheets were synthesized by a chemical precipitation method. The electrochemical properties were studied as supercapacitor electrode materials. NiO hollow microspheres were prepared through a water bath method. The gas-sensing performances to volatile organic compound vapors were tested. Ni(OH)2/Ni composites were synthesized by hydrothermal method, and the adsorption properties were tested to azo dye Congo red (CR). The main contents and results are summarized as follows:(1) Synthesis, characterisation and electrochemical properties of Ni(OH)2and NiO nanosheets as supercapacitor electrode materialsThe flower-like Ni(OH)2nanosheets were synthesized by chemical precipitation method using cetyltrimethylammonium bromide (CTAB) as cationic surfactant at room temperature. The Ni(OH)2nanosheets were converted to NiO nanosheets via calcination under appropriate conditions. Analytical methods such as XRD, SEM, TEM, FTIR measurements were employed to characterize the morphology and microstructure of the final products. The electrochemical properties of Ni(OH)2and NiO nanosheets were studied as supercapacitor electrode materils. The results show that Ni(OH)2and NiO nanosheets have good stability and high specific capacitance. The electrochemical properties of the sample annealed in furnace at250℃for24h are the best of all. The specific capacitance is550F/g at current density of1A/g.(2) Preparation, characterization and gas-sensing properties of NiO hollow microspheres for volatile organic compound vaporsNiO hollow microspheres were prepared by water bath method. The structural characterizations included XRD, SEM, TEM and XPS were used to examine the morphology and microstructure of the final products. The formation mechanism is also explored. The gas-sensing properties of the resulted NiO hollow microspheres for volatile organic compounds (VOCs) were investigated. The sensor based on NiO hollow microspheres shows high gas response, fast response and recovery toward VOCs gas. For its high specific area, it shows the highest gas response of33for isopropanol with the concentration of600ppm at the operating temperature of220℃.(3) Synthesis and characterisation of Ni(OH)2/Ni composites and their adsorption properties of Congo red in aqueous solutionNi(OH)2/Ni composites were synthesized by a hydrothermal reduction method using ethylene glycol (EG) as reducing agent. The samples were characterized and analysised by XRD, SEM and TEM. The adsorption properties of Ni(OH)2/Ni composite and pure Ni(OH)2were tested by the adsorption of azo dye Congo red. The as-synthesized Ni(OH)2/Ni composites are found to be effective adsorbents for the removal of Congo red pollutant from wastewater than pure Ni(OH)2. Furthermore, as the Ni(OH)2/Ni composites dispersed in water can be easily attracted using a magnet due to its paramagnetic behavior. The as-synthesized Ni(OH)2/Ni composites could be maintained for at least five runs, which are of great importance for potential practical applications.