Preparation, Electrochemical And Catalytic Performance Of Micro/Nano Hierarchical Porous NiO

NiO micro/nanomaterials with different novel morphology were prepared by hydrothermal/solvent-thermal method. As a control experiment, crystalline NiO nanoparticles with an average diameter of 50 nm were synthesized by co-precipitation method. The microstructure, morphology and specific surface area of the products were studied by employing XRD, SEM, HRTEM and nitrogen adsorption-desorption. The growth mechanism of micro/nano hierarchical porous NiO was investigated preliminarily, and the applications of the micro/nano hierarchical porous NiO in the lithium-ion batteries, super capacitors and catalysts were also studied. The detailed works can be summarized as follows:1. Micro/nano hierarchical porous Ni2(CO3)(OH)2 microspheres were synthesized via a hydrothermal method in a nickel salts/precipitant/template agent/water reaction system at the reaction temperature of 100℃for 12 h. Furthermore, micro/nano hierarchical porous urchin-like NiO microspheres were successfully prerared by annealing treatment of the Ni2(CO3)(OH)2 microspheres. The microstructure, morphology and specific surface area of the products were studied by employing XRD, SEM, HRTEM and nitrogen adsorption-desorption. The results showed that large quantity of nanoneedles with a mean diameter of 30-40 nm self-assembled into an urchin-like NiO microsphere with numerous nanopores of 5-20 nm on the surface. The maximum BET surface area of the urchin-like NiO microspheres can reach as high as 325.238 m2/g with a pore volume of 0.338 cm3/g. Moreover, its electrochemical specific capacity performance was investigated by means of charge-discharge measurement. The results indicated that the micro/nano hierarchical porous urchin-like NiO delivered a large first discharge capacity of 968.0 mAh/g under a voltage ranging from 0.5 V to 3.0 V at a rate of 0.1 C, which was much superior to that of the synthesized NiO nanoparticles (792.8 mAh/g) by co-precipitation method.2. Micro/nano hierarchical porous (3-Ni(OH)2 microspheres were synthesized via a solvent-thermal method in a nickel salts/precipitant/template agent/binary solvent reaction system at the reaction temperature of 100℃for 12 h. Furthermore, micro/nano hierarchical porous flower-like NiO microspheres were successfully prepared by annealing treatment of the (3-Ni(OH)2 microspheres. The microstructure, morphology and specific surface area of the products were studied by employing XRD, SEM, HRTEM and nitrogen adsorption-desorption. The results showed that a large quantity of nanoplates with a mean width of 200-500 nm,thickness of 5-10 nm self-assembled into a flower-like NiO microsphere. The maximum BET surface area of the flower-like NiO microspheres can reach as high as 213.762 m2/g with a pore volume of 0.497 cm3/g. Moreover, its electrochemical specific capacity performance was investigated by means of charge-discharge measurement. The results indicated that micro/nano hierarchical porous flower-like NiO delivered an extraordinary large first discharge capacity of 1636.2 mAh/g under a voltage ranging from 0.5 V to 3.0 V at a rate of 0.1 C, which was also far greater than that of the synthesized NiO nanoparticles (792.8 mAh/g) by co-precipitation method.3. The prepared NiO nanoparticles were utilized as a catalyst for preparing one-dimensional carbon nano-materials via an ethanol catalytic combustion process. The results showed a large proportion of helical carbon mirofibres have been produced than that in traditional reaction using NiCl2 as catalyst.